Medical device

ABSTRACT

A medical device for example a wound dressing having antibacterial and optionally, antifungal properties, are provided together with methods for making the device. An exemplary dressing includes a layer of silver-containing fabric, (optionally) a layer of absorbent material, and (optionally) a layer of flexible air-permeable and/or water-impermeable material. The dressing can be used for prophylactic and therapeutic care and treatment of skin infections and surface wounds (including surgical incisions), as a packing material, and as a swab for surface cleaning.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/255,492 filed Oct. 21, 2005, which is a continuation-in-part of U.S.patent application Ser. No. 10/421,370, filed on Apr. 23, 2003, whichclaims priority to U.S. Patent Application 60/374,769, filed Apr. 23,2002, which is a continuation-in-part application of U.S. patentapplication Ser. No. 09/531,245, filed on Mar. 21, 2000, now U.S. Pat.No. 6,861,570, and is a continuation of PCT/US98/19689 filed on Sep. 22,1998, which is a continuation-in-part of U.S. patent application Ser.No. 08/935,026, now U.S. Pat. No. 6,087,549; this application is acontinuation-in-part of U.S. patent application Ser. No. 08/707,779filed on Sep. 03, 1996, now U.S. Pat. No. 7,005,556, which is acontinuation-in-part application of U.S. patent application Ser. No.08/524,134, filed Sep. 05, 1995, now abandoned, which is acontinuation-in-part of U.S. patent application Ser. No. 08/623,046,filed Mar. 28, 1996, now U.S. Pat. No. 5,814,094; this application is acontinuation-in-part of U.S. patent application Ser. No. 10/660,209,filed on Sep. 11, 2003, which is a continuation application of U.S.patent application Ser. No. 09/531,245, filed Mar. 21, 2000, now U.S.Pat. No. 6,861,570; this application is a continuation-in-part of U.S.patent application Ser. No. 09/613,961 filed on Jul. 11, 2000, now U.S.Pat. No. 7,214,847, which is a continuation-in-part of U.S. patentapplication Ser. No. 08./935,026 filed on Sep. 22, 1997, now U.S. Pat.No. 6,087,549, and all of which are incorporated by referenced in theirentirety.

BACKGROUND

1. Technical Field

The disclosure generally relates to a medical device for the care ortreatment of a pathology. In particular, the disclosure relates to awound dressing, for example conductive wound dressings havinganti-microbial, therapeutic or prophylactic properties, and methods formaking the dressings.

2. Related Art

The treatment of wounds has become a highly developed area of scientificand commercial investigation because increased rates of healing reduceshealthcare costs and decreases the risk of complications due tosecondary infections. It is currently believed that healing is relatedto the degree of injury, the immunological and nutritional status of thehost, contamination of the wound, the maintenance of the moisture level,pH and oxygen tension of the wound surface, and the electricalparameters of the wound site in relation to the surrounding intact,uninjured tissue. In particular, regeneration in amphibians and fracturehealing in mammals are associated with complex changes in the localdirect current (DC) electric field. It is believed that the electricfield gradually returns to normal pre-injury levels as the injury heals.Conversely, failure of the normal healing process, for example as infracture non-unions, is associated with, among other things, the absenceof appropriate electrical signals at the site of the injury orinfection.

There have been numerous studies conducted on wound healing inamphibians because their rate of healing is significantly greater thanthat of mammals. Wound healing in mammalian skin occurs over days oreven weeks, with epithelial cell migration rates ranging from 7 (drywound) to 20 (wet wound) micrometers/hour. Amphibian skin wounds healwithin hours, with epithelial cell migration rates ranging from 60 tomore than 600 micrometers/hr. The expedited rates of healing inamphibian skin may be partially explained by the aqueous environmentthat bathes the outer surface of the epithelium. Amphibian wounds in anaqueous environment are provided with the appropriate ions tore-establish the electrical potential on the surface of the wound aswell as provided with an environment favorable to cell migration andreproduction.

It is generally recognized that dry wounds in mammals heal more slowlythan wounds that are kept moist by occlusive dressings. Keeping theepidermis surrounding a wound and the wound itself moist stimulates thewound to close. Wound dressings have been designed to retain moisturefrom the exudates produced by the wound and function by preventingevaporation of fluid. Wounds that are dry and lack production of□bsorben must depend upon the moisture within a self contained wounddressing. If the wound dressing dries out, the needed moisture level foroptimum wound healing will not be maintained and the dressing will stickto the wound surface and cause disruption of cellular processes. Thelack of moisture often results in the formation of an eschar or scab,and a general slowing of the wound healing process.

Wounds that produce an extensive amount of moisture are thought tocreate another problem called skin maceration. Skin maceration is asoftening of the skin or wearing away of the skin as a result ofcontinual exposure to bodily fluids or moisture. It is known to cause abreakdown of the cornified epithelium, thereby reducing the physicalmicrobial barrier function as well as the moisture regulation functionof the epidermis. With a reduction of the microbial barrier function,the wound surface has a significantly greater risk of contamination bypathogenic microbes from the surrounding environment. Therefore, it iscommon practice to design wound dressings to reduce or prevent skinmaceration by wicking away wound fluids and storing the fluids inabsorbent layers.

A common practice in the treatment of wounds is the application ofimpermeable backing sheets to a wound dressing. The backing sheetfunctions as a moisture retention layer as well as a physical barrier toprevent microbial penetration. The backing sheet typically consists of amaterial with specified moisture vapor transmission rates (MVTR) andprovides control of the rate of evaporation of moisture from theabsorbent layer. Therefore, the backing sheet is generally impervious toliquid.

There are a variety of venting systems that can be contained within thedressing structure for the purpose of directing wound exudates viaspecific pathways to provide a controlled leakage of fluids from thewound surface to a contained absorbent layer.

For example, in certain perforated films, the perforations aresufficient to permit wound exudates to diffuse through the film at arate that precludes pooling on the wound surface, which is a commoncause of maceration. These dressings must be removed when they becomesaturated with exudates.

While there are numerous dressings designed to retain the moisturecontent of wounds, there are still many areas of inefficiency in currenttreatment methods. For example, these dressings are only effective formoist wounds and do not provide any significant benefit for dry wounds.Wounds vary significantly in the amount of exudates or moisture producedthroughout the healing cycle. In order to maintain an effective level ofmoisture it is necessary to continually change the dressings as theabsorbent component reaches maximum capacity. Conversely, it isnecessary to remove the dressings and add fluid to dry wounds, thenreplace the dressings. In either situation, removal of the dressing cancause disruption of the cellular process of the wound and increase therisk of contamination by microbes.

Furthermore, it is necessary to change the types of dressings throughoutthe healing process of the wound as the moisture content changes.

Besides the effect of moisture on wound healing, microbial growth at thesite of injury has a great effect on healing. In normal skin, amicrobial barrier is created by the cornified epithelium. Wounds causedestruction of the cornified epithelium as well as deeper layersthereto, and the loss of the natural anti-microbial barrier.

The presence of microbial species at the wound site creates a bioburdenthat can retard the healing process. As the bioburden of the wounddecreases to bacterial counts less than 103 CFU/ml, wound healing isenhanced. Treatment of wounds typically involves preventingcontamination by pathogenic microbes from the external environment aswell as reducing the microbial bioburden of the wound.

While there are many antibacterial and antifungal agents that can beused to treat wounds, the anti-microbial and antifungal properties ofsilver have been of particular interest. However, the effectiveness ofsilver as an anti-microbial agent is at least partly determined by thedelivery system. Most silver compounds that dissociate readily andproduce large numbers of free silver ions are highly toxic to mammaliantissues. Less-toxic compounds, including silver sulfadiazine cream,widely used in the treatment of burns, do not dissociate readily andtherefore do not release large numbers of silver ions. Therefore, thesecompounds must be re-applied frequently to maintain their clinicalefficacy.

Silver has been used in the construction of wound dressings to activelyor passively release metallic silver particles or silver ions into thewound. Active release of silver ions require the presence of anelectrical potential that actively drives silver ions from a source intothe wound dressing or wound itself. This has been accomplished with abattery or other power source known to those skilled in the art. Passiverelease of silver ions is dependent upon the solubility of silver inaqueous solutions. The passive release of silver ions has been calledthe oligodynamic release process and includes the passive dissolution ofsilver into a solution.

The anti-microbial efficiency of metallic silver or silver ions isdependent upon the microbe coming into direct contact with the surfaceof the metallic silver or coming into contact with a released silverion. Therefore, the total surface area of metallic silver and the numberof silver ions released is directly related to the level ofanti-microbial activity.

Various methods have been used to create mechanisms for metallic iontransfer.

For example, the vacuum vapor deposition technique has been utilized inthe construction of wound dressings to plate metallic silver and silversalts onto a variety of substrates. The vacuum vapor depositiontechnique has been modified so as to create “atomic disorder” of theplated silver that has been reported to enhance the anti-microbialeffect by allowing the release of nanocrystalline particles of metallicsilver. However, the technique provides a flat plating pattern and doesnot uniformly coat the entire three-dimensional surface of fibers.

Another mechanism used for passive release of silver ions and particlesfrom a wound dressing includes imbedding or placing silver particles ofvarying sizes in a variety of substrates. Finely divided metallic silverin collagen has been incorporated into surgical dressings ofreconstituted collagen foam laminated to a thick continuous layer ofinert polymer. This does not allow for direct contact of the maximumnumber of ions with the wound.

When connected to a voltage source, a metal anode and a return electrodehave been used as a means to deliver silver ions iontophoretically to awound or within a wound dressing. Electrically conductivesilver-impregnated meshes, including silver-protein colloids, have beendisclosed with current densities as low as IOIA/mm2. This requires anexternal power source and stationary equipment and is cumbersome for thepatient.

Silver foils have been incorporated into wound dressings as a means ofsupplying silver ions as an anti-microbial agent, as well as acting asan electrode for dispensing medications. In addition, silver has beenfabricated into devices that incorporate a means of applying atherapeutic voltage to the wound. Foils do not provide for circulationof air, and are limited in surface area.

Compounds that slowly release silver into the wound environment havebeen disclosed in substances such as water soluble glass, phosphoruspentoxide and silver oxide.

The silver impregnated glass may be in the form of a powder, granules,or woven into a dressing. The water soluble glass releases silversecondary to the dissolution of the glass.

Such compositions have a high volume resistance and very poorconductivity.

Regardless of whether silver is provided in the form of silver ions oras a topical composition (silver nitrate solution, silver sulfadiazinecream, or the like), its beneficial effects are manifested primarily atthe treated surface and immediately adjacent tissues, and are limited bythe achievable tissue concentration of silver ions. Despite theavailability of numerous techniques for the delivery of silver andsilver compounds in vitro and in vivo, there remains a need for adelivery system that is capable of supplying clinically usefulconcentrations of silver ions to a treatment site without the need foradjuvant electrical stimulation.

None of the available metallic ion treatment devices provide anefficient and convenient means to restore the homeostaticelectromagnetic environment for areas of wounds. They also do notprovide for maximum surface area for release of metallic ions. Inaddition, the prior art does not address the need to regulate themoisture content of a wound without manually changing the dressings, orapplying liquids or medicants. This is true in part because of thebelief that a wound dressing must serve as a microbial barrier andprevent the movement of fluids from the wound exudates. The currentlyavailable treatments for wounds prevent microbial contamination byproviding a physical barrier which must be manipulated and interruptedas part of the treatment process. Such activities allow for microbecontamination and interrupt the healing process.

It is believed that wound healing occurs with maximum speed andefficiency when the wound is maintained in a moist condition withoutexcessive wetness or dryness.

Negative pressure or sub-atmospheric pressure has been used incombination with wound dressings for the treatment of soft tissue damageand wound closure. Negative pressure wound therapy assists in woundclosure by applying localized negative (sub-atmospheric) pressure tohelp promote wound healing. Generally, vacuum pressure is applied to aspecial dressing positioned in the wound cavity or over a flap or graft.This pressure-distributing wound packing helps remove fluids from thewound and promote the normal healing process.

Some negative pressure therapies use open-cell reticulated foam that canbe cut to the shape of the wound, or can be placed side by side orlayered to treat very large wounds. A tube in contact with the foamallows the application of vacuum pressure for the removal of excesswound fluid. The dressing and distal evacuation tube are covered by atransparent, occlusive drape that provides a seal which allows theapplication of vacuum pressure to the system.

The free end of the evacuation tube is attached to a canister reservoir,which fits into a microprocessor-controlled vacuum unit and collects thefluids drawn away from the wound. The vacuum unit provides continuous orintermittent negative pressure selected to meet the needs of the woundbeing treated. The pressure can be adjusted within a range that has beendemonstrated to provide optimal fluid removal without placing thedelicate wound tissue at risk of injury.

The application of negative pressure therapy to a wound provides a moistwound-healing environment. A moist wound-healing environment is thestandard of care for wound healing. Removal of excess interstitial fluidalso can lead to removal of excess proteinases present in the periwoundenvironment. Metalloproteinases are known to bind and degrade growthfactors before the growth factor can reach its target tissue. Withinhibitors removed, growth factors can stimulate cell proliferation andmigration. Removal of excess interstitial fluid can naturally helpdecrease periwound induration (swelling) further helping to promotewound healing.

Problems associated with applying a negative pressure to a woundinclude: tissue growth into the dressing; potential damage of delicatestructures such as blood vessels and internal organs and adhesion of thedressing to the wound base causing repeated trauma (therefore increasingpain and increased healing time) with dressing changes.

Accordingly, there is a need for additional devices and methods fortreating or preventing a pathology.

SUMMARY

Aspects of the present disclosure generally relate to compositions andmethods for treating a pathology of an organism. An exemplary devicecomprises at least one conformable, conductive layer comprising one ormore fibers or foams, wherein the one or more fibers or foams are coatedwith an antimicrobial metal in an amount sufficient to provide theconductive layer with a surface resistance of less than about 1,000ohms/cm² or less, 5 ohms/cm² or less, or 1 ohm/cm² or less and whereinthe at least one layer comprises a plurality of apertures sufficient toprovide the device with a liquid wicking value of at least about 5%. Inother aspects, the device can have a liquid wicking value of at leastabout 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%,75%, 80%, 85%, 90%, 95% or more.

In certain aspects, the disclosed compositions can aid in restoring thetransepithelial skin potential, maintain a moist wound healingenvironment, create a functional microbial barrier, reduce microbialbio-burden of the wound, deliver an antimicrobial metal, aid in reducingpain, or a combination thereof. For example, certain embodiments of thedisclosed devices can reduce the wound potential or make the woundpotential more negative by about 1 mV, about 5 mV, about 10 mV, about 20mV, about 30 mV, about 40 mV, about 50 mV or more.

The present disclosure also provides devices, medical devices, wounddressings and methods of using the disclosed compositions. Devices suchas wound dressings of the present disclosure comprise one or more layersof materials. One of the layers can be a layer comprising conductivefibers, non-conductive fibers, conductive foams, non-conductive foams orcombinations thereof. This layer, referred to as the conductive layer,comprises fibers, foams or a combination of fibers and foams that havefrom approximately 0% to approximately 100% of the surface or surfacesof the fiber or foam covered with a metal plating, and all ranges therebetween. In certain aspects, one or more fibers or foams are coated withan amount of antimicrobial metal effective to provide the conductivelayer with a surface resistance of about 1,000 ohms/cm² or less,typically, about 5 ohms/cm² or less, even more typically about 1 ohm/cm²or less. Fibers or foams that do not have metal plating are referred toas nonconductive and fibers or foams with metal plating are referred toas conductive.

Another aspect provides a device having at least two layers ofconformable conductive fabric separated by a plurality of supports.Other devices of the present disclosure can comprise a second layer thatis an absorbent layer as well as an optional third layer that is amoisture control layer, which may be impermeable to gases or liquids ormay have apertures therein that allow transmission of differingmaterials such as gases, liquids or microbial or environmentalcontaminants.

Preferably, the at least one conductive layer can be placed in contactwith a wound. At least a portion of the conductive layer comprisessubstrates coated with metal. Fibers include but are not limited topolysaccharides, for example alginates, chitosans, natural or syntheticpolymers, such as polyamides, polyesters, silk, cotton, proteins, or acombination thereof. Fibers may vary in composition and threedimensional structure.

A preferred conductive layer comprises a plurality of fibers wherein atleast one fiber comprises a three dimensional structure and the fiber issubstantially coated with a metal.

Another preferred conductive layer comprises a polymeric foam structurewherein at least a portion of the foam surfaces are substantially coatedwith a metal, or the layer comprises a combination of fibers and foams.The plurality of fibers or foams within the conductive layer comprise atleast one fiber or foam, having its surfaces coated with metal andinclude fibers or foams that are shaped to provide a spontaneousmovement of fluids such as capillary action or wicking of fluids. Suchfibers or foams are designed with grooves or channels along thelongitudinal axis of the fiber or foam and these channels serve as ductsto move fluids, store or trap substances and provide a large surfacearea for a given denier per fiber or surface area of a foam.

Preferably, additional layers of the dressing include at least oneabsorbent layer and at least one moisture regulation layer having aplurality of apertures disposed primarily in the moisture regulationlayer. It will be appreciated that one or more of the layers of thedisclosed devices can have one or more apertures. The apertures may varyin size from a layer with no apertures to apertures in a size range thatis occlusive to liquids but not to gases, to a size range that allowsliquids and gases to pass through, to a size that is open to microbes,such as bacteria, viruses, fungi, parasites, and environmentalcontaminants.

An additional aspect of the disclosure relates to wound dressings thatprovide for a capacitive effect formed by the alternation of conductivelayers of fiber with non-conductive layers.

Another aspect of the disclosure relates to wound dressings having aplurality of layers arranged according to the ratio of conductive tononconductive fibers comprising each layer. Additional aspects of thedisclosure relate to various configurations of the functional shape ofthe novel dressings. Another aspect of the disclosure relates to methodsof using the novel dressings to treat wounds in a human or an animal.Further aspects of the disclosure relate to methods of making thedisclosed devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are illustrated in the drawings in whichlike reference characters designate the same or similar parts throughoutthe figures.

FIG. 1 shows a representative wound dressing according to one embodimentof the present disclosure.

FIG. 2 shows another representative wound dressing according to oneembodiment of the present disclosure.

FIG. 3 shows still another representative wound dressing according toone embodiment of the present disclosure.

FIG. 4 shows a representative multilayer wound dressing according to oneembodiment of the present disclosure.

FIG. 5 shows a schematic depiction of a cross-section of woundedmammalian skin with a dressing in accordance with an embodiment of thepresent disclosure positioned over the wounded area.

FIG. 6 shows a graph of voltage verses position on the wounded skin asshown in FIG. 5.

FIG. 7A shows a representative cross-section of polymeric autocatalyticplated fibers on a non-conductive substrate.

FIG. 7B shows a cross-section of one polymeric autocatalytic platedfilament from FIG. 7A.

FIG. 7C shows a portion of the cross-section of one polymericautocatalytic plated filament of FIG. 7B.

FIG. 7D shows an illustration of an enlargement of the metallic surfaceof a polymeric autocatalytically plated filament representingapproximately 62 μm².

FIG. 8 shows a graphic representation of the ionic silver releaseconcentration from an autocatalytically silver plated fabric measured byinductively coupled plasma spectroscopy.

FIG. 9 is a graphic representation of the anti-microbial activity of anautocatalytically silver plated fabric.

FIG. 10A is an illustration of a possible geometric shape for apertures.

FIG. 10B is an illustration of a possible geometric shape for apertures.

FIG. 11 depicts a cross-section of FIG. 10 illustrating one aspect of awound dressing.

FIG. 12 is an illustration of one aspect of an island wound dressing.

FIG. 13 is an illustration of a cross-section of FIG. 12.

FIG. 14 depicts of a cross-section of an alternative aspect of anabsorbent layer.

FIG. 15 represents a cross-section of an alternative aspect of a wounddressing.

FIG. 16 is an illustration of a cross-section of an alternative aspectof a wound dressing.

FIG. 17 illustrates of a cross-section of an alternative aspect of anisland wound dressing.

FIG. 18 is an illustration of a cross-section of a secondary wounddressing.

FIG. 19 is a cross-section of a two-layer autocatalytically metal platedfoam.

FIG. 20 is a cross-section of a one-layer autocatalytically metal platedfoam.

FIG. 21 is a cross-section of an autocatalytic metal plated filamentthat provides spontaneous movement of fluids.

DETAILED DESCRIPTION

Embodiments of the disclosure include compositions for the treatment orprevention of a pathology and methods of their use. One embodimentprovides a medical device useful for the treatment of a pathology in ahuman or animal. An exemplary medical device includes, but is notlimited to single or multilayer wound dressing. Other embodimentsprovide methods of treating or preventing wounds or pathologies andmethods of making the disclosed devices.

In certain embodiments, the disclosed medical devices are configured toaid in healing by (1) assisting with restoration or maintenance of thetransepithelial skin potential; (2) creating an anti-microbial barrierto environmental pathogens without restricting the passage of liquidsand gases; (3) aiding in the regulation of the moisture content at thewound surface and of the dressing and allowing fluids to be manuallyadded or removed, or to be added or removed by means of a secondarydressing; (4) allowing therapeutics or liquids to be added to the wounddressing without disturbing the wound surface; (5) aiding in thereduction of pain originating from the wound; or a combination thereof.

Prior to a detailed discussion the various embodiments, the followingdefinitions are provided to clarify the disclosed subject matter. Thesedefinitions are to be used unless otherwise noted.

1. Definitions

The term “anti-microbial metal” refers to a metal, metal alloy, or metalcomposition comprising one or more metals that inhibits, prevents, orreduces the growth or reproduction of a microbe.

The term “fabric” refers to an underlying structure. An underlyingstructure includes, but is not limited to a substrate made by weaving,felting, knitting, crocheting, or a combination thereof, natural orsynthetic fibers. The term includes compressed matted animal fibers,natural fibers, synthetic fibers, or a combination thereof.

As used herein, the terms “fiber” or “fibers”, “foam” or “foams” areinterchangeable. Though the terms denote differently formed materials,where one of the terms is used, the other or the plural of either isintended.

The term “Liquid Wicking Potential Value (Liquid Wicking Value)” refersto a performance parameter which pertains to the amount of liquidremoved from a described target area by the disclosed device during avertical wicking operation. This value represents the ability of thedevice to remove fluid from a target area. At least one layer of thedevice is configured to provide the desired Liquid Wicking PotentialValue.

The term “microbe” refers to a minute life form including, but notlimited to bacteria, fungi, RNA or DNA viruses, prions, mycoplasma, andsingle-cell organisms or parasites.

The term “organ” refers to any part of the body of a human or animalhaving a special function including, but not limited to, bone, muscle,skin, heart, eyes, liver, kidney, vascular system, lungs, reproductiveorgans, and the like. The term wound can also refer to any abnormalcondition of an organ of a human or animal that results from mechanicalor physiological events or conditions.

The term “three dimensional coating” refers to the circumferential,concentric, uniform coating of all the surfaces of a fiber or foam whichmay be the entire length of the fiber or foam or may comprise one ormore coated sections of the fiber or foam.

The term “wound” or “pathology” are used interchangeably and refer toany wounds, internal or external to the body of a human or animalincluding, but not limited to, unbroken or broken skin, bruises,hematomas, inflammation, lesions, rashes, blisters, pustules, abrasions,hives, dermal eruptions, partial thickness wounds, partial thicknessburns, incisions, skin graft sites, skin donor sites, lacerations, StageI-IV dermal ulcers, venous stasis ulcerations, pressure ulcerations,arterial insufficiency ulcerations, diabetic ulcers, decubitus ulcers,organ lacerations, organ abrasions, organ tears, or external andinternal surgical wounds.

2. Embodiments

One embodiment provides a device for the treatment or prevention of apathology comprising a first conformable, conductive material or fabriccomprising: (1) an anti-microbial metal; (2) a surface resistance ofless than about 1,000 ohms/cm²; and (3) a plurality of apertureseffective to provide the device with a liquid wicking value of at leastabout 5%. In other embodiments the device can have a liquid wickingvalue of at least about 10%, 15%/20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%,60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or more.

Liquid wicking value can be determined as described in U.S. Pat. No.6,437,214 which is incorporated by reference in its entirety. Briefly,the following test is used to determine the capability of a material toremove liquid from a target area. Allow the device to absorb an amountof liquid from a reservoir and determine the amount of liquid that hasbeen removed from the target area. Determine the wet weight of thedevice. Dry the device and subtract this weight from the wet weight todetermine the amount of liquid which moved out from the target area.Divide the amount of liquid removed from the target area by the totalamount of liquid applied to the target area (e.g., target zone surfacearea in cm², multiplied by 1 g of liquid per cm²); and multiply thatresult by 100. This is the Liquid Wicking Value of the layer region.

The liquid wicking value of a multi-layer device or dressing is thelargest liquid wicking value provided by any one of the layers. Forexample, the liquid wicking value of a two-layer, device is the largerof the two liquid wicking values provided by the two layers.

Certain embodiments provide devices or dressings that control themoisture levels of the wound surface including controlling the moistureloss, altering the aperture or slit configuration of the dressing;altering the materials of the wound contact layer; altering theabsorbent characteristics of one or more absorbent layers. Absorbentlayer materials include, but are not limited to, hydrogels, chitins,alginates, polyurethane foams, acrylates, hydrocolloids, collagens,gauze, cotton, and cellulosic materials.

Certain embodiments of the disclosed devices are useful with negativepressure therapies. In these embodiments, the device is configured withapertures that provide at least about 10% liquid wicking value andfacilitate the generation of a vacuum without becoming blocked by fluidin the wound. The dressings advantageously release ionic silver whichprevents, reduces, or treats infection of the wound.

Another embodiment provides a medical device comprising at least onelayer of conformable, conductive material. The conformable, conductivematerial can also be absorbent material and/or moisture retentionmaterial. Alternatively, the medical device can have an optional layerof absorbent material in contact with the conformable, conductivematerial. Generally, the conformable conductive material is a fabric,including a felt. The device can have at least one layer, at least twolayers, at least three layers, at least four layers, at least fivelayers, at least six layers, at least seven layers at least eightlayers, at least nine layers, at least ten layers, and more.

Still another embodiment provides a device comprising a conductivefabric or material wherein the conductive fabric or material comprisesan anti-microbial coated foam. The coated foam can provide theconductive material with a surface resistance of less than about 1,000Ω/cm². The foam can also be flexible or conformable or can beconventional foams known in the art.

Conventional foams, produced by traditional methods of foam formation,have voids or pores ranging from 50 to 100 microns in diameter. By somedefinitions, microcellular foams are those containing cells less than 50microns in diameter. However, in the specification and claims, materialsreferred to as microcellular foams are those foams containing voids orpores of varying geometries, that are suitable for biomedicalapplications. Such foams preferably contain pores or voids withdimensions of from about 1 to about 400 microns, most preferably fromabout 5 to about 200 microns.

Foams of the disclosed devices may be made from suitable organicpolymeric materials, including the bioabsorbable and non-bioabsorbablethermoplastic polymers. The non-bioabsorbable medically significantpolymers include the polyamides, polyesters, and polyolefins. Thebioabsorbable polymers include poly(dioxanone), polyglycolic acid,polylactic acid, polyalkylene oxalates, polyanhydrides and copolymersthereof.

Depending upon the polymer selected and the size and distribution ofvoids or pores within the foam, the foams may range in mechanicalproperties from flexible to semi-flexible to rigid. Thus, foams incertain embodiments may be tailored for specific uses by judiciousselection of polymer, and void or pore size, depending upon the intendeduse of the foam construct.

FIG. 1 shows an exemplary embodiment of the disclosed medical device orwound dressing. The wound dressing 100 has at least one layer comprisinga conformable, conductive substrate 10. Substrate 10 comprises fibers,yarns, foams, synthetic or natural polymers, or combinations thereof.One embodiment provides a conformable, conductive substrate comprising aplurality of yarns or fibers. A yarn can comprise one or more fibers,foams, or polymers. An exemplary yarn comprises a nylon fiber having anelastic component wrapped or twisted around the fiber. The elasticcomponent can be any elastomeric substance including, but not limited toSPANDEX®, LYCRA® or elastomeric fibers, for example fibers having along-chain synthetic polymer comprising at least 85% of a segmentedpolyurethane. Generally, the fiber is selected from a substance that canbe autocatalytically covered with an anti-microbial metal such assilver, and the elastomeric fiber is selected from an elastomere that isnot covered with an anti-microbial metal during the autocatyliticprocess. Thus, one embodiment provides a conformable, conductivesubstrate comprising one or more yarns, wherein at least one yarncomprises a fiber coated with anti-microbial metal in combination with asecond fiber that is not coated with the anti-microbial metal. In oneembodiment, at least one layer comprises less than about 15% ofelastomer, typically less than about 10%, more typically about 3% toabout 7% of an elastomer. The yarns or fibers can be woven, non-woven,knitted, entangled, or otherwise combined to produce a substrate, forexample a fabric or felt.

The fibers or foams of the yarn can be multi-lobular or grooved.Typically, the fiber coated with the anti-microbial metal ismulti-lobular or grooved. The multi-lobular or grooved fibers increasethe surface area of anti-microbial metal exposed to the wound as well asaid in fluid movement by generating or promoting capillary action in thesubstrate.

Substrate 10 optionally includes a plurality of apertures 11 positionedin the substrate to provide a liquid wicking value of at least about 5%,10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, or more. The apertures can also be positioned in thesubstrate to facilitate the formation of a vacuum when used inconjunction with negative pressure treatment. For example, the aperturescan be position in substrate 10 to uniformly apply the substrate to awound when under negative pressure.

FIG. 2 shows an alternative embodiment of the disclosed devicecomprising rectangular apertures 12 and oval or circular apertures 11.The apertures can be configured in any geometric shape. In someembodiments, the apertures are shaped to facilitate delivery ofexogenous substances including, but not limited to therapeutic agentssuch as antibiotics, anti-inflammatory agents, anti-oxidants,antibodies, nutrients, collagen, autologous tissue, autologous cells,recombinant cells, growth factors, stem cells, adult stem cells, adiposestem cells, bone marrow cells, or umbilical cord blood cells. It will beappreciated that the conductive, conformable fabric can optionallycomprise one or more mammalian cells, for example mesoderm, endoderm, orectoderm cells. The cells can be transfected to express at least onetherapeutic protein or polypeptide including, but not limited to acytokine, chemokine, growth factor, polypeptide hormone, or a fragmentthereof.

FIG. 3 shows an exemplary multilayer device comprising substrate 10 andrectangular apertures 12. Substrate 10 is laminated or attached to anabsorbent layer 14 by an adhesive 13. Absorbent layer 14 can be a secondlayer of conformable conductive material as described above, or cancomprise natural fibers such as cotton or wool, absorbent syntheticfibers, foam, gauze, sponge, or combinations thereof.

FIG. 4 shows another embodiment in which two layers of conformableconductive fabric are separated by a plurality of supports 15. Thesupports can be coated with an anti-microbial metal or the supports canbe uncoated. In certain aspects, the supports comprise a syntheticpolymer such as a polyamide or nylon.

FIGS. 3 and 11 show exemplary embodiments of a wound dressing. FIG. 11shows a wound dressing comprising at least one conductive layer, atleast one absorbent layer positioned adjacent the conductive layer oradjacent to a moisture regulation layer, and at least one moistureregulation layer positioned adjacent to the absorbent layer or adjacentto the conductive layer and comprising a plurality of apertures ofvarying sizes disposed substantially throughout and in the moistureregulation layer.

In some embodiments, at least a portion of the conductive layercomprises fibers or foams coated with a metal, wherein in a range offrom approximately 0% to approximately 100% of the surfaces of thefibers or foams are coated. The fibers or foams may have areas of thelength of the fiber or foam that are coated in a range of fromapproximately 0% to approximately 100% of the surfaces. For example, ina 3 inch fiber, the first inch is uncoated, the surface or surfaces ofthe second inch is 100% coated, and the third inch is uncoated. It willbe appreciated that the fibers or foams are optionally coated with anamount of an anti-microbial metal sufficient to provide the conductivelayer with a surface resistance of less than about 1,000 Ω/cm².

Uncoated or non-conducting fibers and foams, including but not limitedto alginates, chitosans, polymers, synthetic and naturally occurringfibers or foams may be placed in the conductive layer. The metal-platedfibers and foams and the nonconductive fibers and foams vary incomposition and may or may not have a functional three dimensionalstructure used for movement of fluid. A layer may include, but is notlimited to a plurality of fibers wherein at least one fiber is coatedwith a metal, or a layer may include a polymeric foam wherein at least aportion of the foam comprises a three dimensional coating of a metal,and preferably, a uniform coating of metal. The plurality of fiberswhere in at least one fiber comprises a three dimensional coating of ametal may also include fiber or foam shapes that provide movement offluids, such as capillary action or wicking of fluids. The fibers orfoams are designed with grooves or channels along the longitudinal axisof the fiber or foams and serve as ducts to move fluids without apumping means, such as in capillary action, store or trap substances andprovide a large surface area or an active surface area for a givendenier per filament or foam. The term “three dimensional coating” refersto the circumferential, concentric, uniform coating of all the surfacesof a fiber or foam which may be the entire length of the fiber or foamor may comprise one or more coated sections of the fiber or foam.Preferably, during treatment, the dressing can be positioned with theconductive layer in contact with a wound, or with the absorbent layer incontact with the wound.

The base substrate that is coated with a metal to form the conductivelayer can be any biocompatible, flexible, synthetic or natural materialthat can be formed into a film, fiber, foam, web, or any configurationcapable of supporting a metal coating and combinations of such forms.The base substrate materials can include, but is not limited to carbon,polyamides including but not limited to nylon 6 or nylon 6,6, glass,KEVLAR®, acetate, flax, olefin, polyethylene, rubber, saran, spandex,vinyl, polyester, silk, wool, rayon, cotton, cellulose or combinationsthereof.

Configurations include fibers, films, foams or webs comprising blends,composite materials, or multi-component fibers, either woven, knitted ornon-woven. Some individuals may have a topical hypersensitivity tocertain fiber materials, and the base fiber is preferably non-allergenicor hypoallergenic. It is to be understood that for purposes ofillustration, the discussion refers to fibers for the conductive aspectof the disclosed devices, but can also include conductive foams.

A preferred material for making fibers or foams is any material that hasa nitrogen group or a similarly functional group capable of beingsensitized, that is available for sensitizing the material forautocatalytic metal plating. If the material does not have a nitrogengroup on the surface of the material, then a layer of differentmaterial, which provides a nitrogen, can be coated on the foam or fiberprior to sensitizing. For example, cross-linked polyethylene fibers arecoated with polyamide to provide a nitrogen group on the surface of thefibers. The polyamide-coated fiber is then sensitized for autocatalyticmetal plating. Compositions and methods for sensitizing materials forautocatalytic metal plating are known to those skilled in the art andinclude, but is not limited to, tin chloride. After sensitizing thepolyamide-coated fiber, a metal, such as silver, is autocatalyticallyplated onto the fiber. The autocatalytic metal plating preferablyprovides a uniform metal coat to the sensitized section of the fiber.The preceding description also applies to metal plating of a foam.

A further embodiment provides a wound dressing comprising at least oneconductive layer having a surface resistance of less than about 1,000Ω/cm², wherein the at least one conductive layer comprises a fiber orfoam containing a therapeutic substance in addition to an anti-microbialmetal coating, for example a small molecule, protein, or cell. Theadditional therapeutic substance can be coated on to the fiber, can becontained within a pore on the fiber surface, or can be contained withina hollow interior of the fiber such that the therapeutic substance isreleased into the wound when the wound dressing is in contact with thewound.

In other embodiments, the conductive layer comprises fiber tubes orporous fiber tubes which are coated with an antimicrobial metal in anamount sufficient to provide the wound dressing with a surfaceresistance of less than about 1,000 Ω/cm² or 1,000 ohms/sq, typicallyless than about 5 Ω/cm² or 5 ohms/sq. The porosity of the fiber tube canbe configured to increase fluid flow away from the wound, for exampleinto an absorbent layer or to the exterior of the wound dressing. Incertain embodiments, the interior diameter of at least one fiber tube isabout 1000 μm, 500 μm, 400 μm, 200 μm, or 100 μm or less.

A further embodiment provides a wound dressing comprising at least oneconductive layer comprising fiber tubes coated with an amount ofanti-microbial metal in an amount sufficient to provide the wounddressing with a surface resistance of less than about 1,000 Ω/cm²,wherein the fiber tubes have an interior diameter in the range of about500 μm to about 100 μm. The tubes can comprise one or more therapeuticsubstances, for example antibiotics, anti-inflammatory agents,anti-oxidants, antibodies, nutrients, collagen, autologous tissue,autologous cells, recombinant cells, growth factors, stem cells, adultstem cells, adipose stem cells, bone marrow cells, and umbilical cordblood cells, cytokines, chemokines, polypeptide hormone or combinationsthereof.

Methods of producing hollow fibers are known in the art and include butare not limited to coating polymeric substance with an anti-microbialmetal and then contacting the polymer with an agent, for example achelating agent, that causes the polymer to depolymerize. Alternatively,the tubes can be formed by extrusion, moulding, or other conventionalmeans.

Under optimum conditions, the conductive layer (114), when moistened,can be electrically conductive, non-adherent, liquid and gas permeable,porous, and anti-microbial. The conductive layer may contact the surfaceof the wound and the surface of normal tissue surrounding the wound.Ideally, the composition of the conductive layer comprises a pluralityof fibers, wherein at least one fiber is uniformly and concentricallycoated with a metal or metal alloy so that the coating is threedimensional and covers all surfaces of the fiber. Ideally also, theconductive layer comprises a polymeric foam wherein the surface isuniformly and concentrically coated with a metal or metal alloy so thatthe coating is three dimensional and covers all surfaces of the foam.All or part of the fiber or foam can be coated three-dimensionally.Preferably, all or a plurality of the surface area of the fibers or foamof the conductive layer (114) are auto-catalytically plated with metalto allow for a uniform, three dimensional coating of the metal or metalalloy and provide the maximum surface area for release of metallic ions.The anti-microbial activity of released metallic ions and the metallicsurface function as a microbial barrier, and aid in preventing themigration of microbes from the surrounding environment to the woundsurface, while at the same time allowing fluids and gases to passfreely.

Any metal or metal alloy capable of being plated onto a substrate toform a conductive layer can be used. Metal elements suitable for thepresent disclosure include, but are not limited to, platinum, copper,gold, nickel or silver, and/or binary alloys of platinum, nickel, cobaltor palladium with phosphorus, or binary alloys of platinum, nickel,cobalt or palladium with boron. In one preferred aspect of the presentdisclosure the metal is silver. For purposes of explanation, silver isused, though it can be substituted with any other metal or metal alloy.Generally, a metal that has anti-microbial properties is preferred.

One embodiment provides devices having a conductive layer that comprisesareas of the layer having metals that provide a permanent orsemi-permanent magnetic field. In a conductive layer, if a current isgenerated by the movement of metal ions, particularly under moistconditions of fluid flow, an electric field and a transitory magneticfield are generated. By providing areas of the layer with particularmetals, such as isotopes of cobalt, a semi-permanent or permanentmagnetic field can be provided to the wound site. This magnetic field isnot dependent on the fluid flow or generation of a current, but providesa steady magnetic field. Though not wishing to be bound by anyparticular theory, it is believed that a magnetic field held in place ata wound aids in the healing processes.

Ideally, the metallic silver used for the disclosure is of high purity,preferably from about 99.0% to about 99.6% pure, although lower puritylevels can also function. It is believed that high purity reduces thelikelihood that contaminants or undesirable ions may contact orpenetrate the wound or skin.

Preferably, the substrate can be in the form of fibers. The range ofdenier of the fibers can be from about 0.0001 denier to about 10,000denier, preferably from about 1.0 denier to about 1000 denier, and morepreferably from about 5 denier to about 300 denier.

The various cross-sectional shapes that may be imparted to individualfibers are known to those skilled in the art, and include, but are notlimited to, round, oval, kidney-bean, dogbone, flat, tri-lobal, andmulti-lobal. Advantageously, a multi-lobal fiber such as the 4DG fibercommercially available from Fiber Innovation Technology Inc of JohnsonCity, Tenn. can increase the surface area by 250% to 300% compared toround fibers. Fiber configurations that are capable of spontaneouslytransporting water on their surfaces are also available and include anumber of fibers similar to the 4DG fiber. In general, while not wishingto be bound to any particular theory, it is believed that the greaterthe surface area of the fiber, the greater the surface area of metallicplated fibers, forming an active surface area, which can result ingreater release of metallic ions and a more effective dressing.

Individual fibers may be fabricated into several different types ofyarns including, but not limited to, spun yarns, filament yarns,compound yarns, fancy yarns, and combinations thereof. Fibers can beconfigured into tow and floc and can be provided in the form of stapleor bulk continuous filament. The filament and compound yarns thatexhibit multiple longitudinal filaments are preferred. It is believedthat the greater the continuity of the yarns, the greater the potentialfor excellent conductivity when plated. Fibers and/or yarns can beassembled into fabrics, including but not limited to, woven fabrics,twisted and knotted fabrics, knit fabrics, non-woven fabrics, felt, andcompound/complex fabrics. It is proposed that the total surface area ofthe fibers that compose the filaments, fibers, yarns or fabric is avariable in determining conductivity as well as passive metal ionrelease into aqueous fluids

In certain embodiments, the autocatalytically metal-plated surfaces havea broad range of surface resistance from about 1,000 kilo ohms/sq toabout 0.0001 ohms/sq, a middle range from about 10 kiloohms/sq to about0.001 ohms/sq and an optimal range from about 10 ohms/sq to about 0.1ohms/sq. It will be appreciated that surface resistance can also beexpressed in ohms/cm² or ohms/in². It is believed that resistancedecreases with increasing numbers of plies or fibers within a layer.Preferably, beyond four plies of conductive fabric, the resistancedecrease may become non-appreciable from a clinical point of view,although the resistance may continue to decrease with additional layers.The preferable upper limit of the number of plies of conductive fabriccan be about ten. Cost, thickness, composition, fiber density and weavestructure and other factors may also be considered in selecting thenumber of plies. A more dense fabric design may need only one ply toachieve the same resistance measurement as a fabric having more than oneply of a highly absorbent material that is less dense. The reduction ofthe surface resistance of the conductive layer can relate to the mannerin which the fabric is plated and secondarily to how the layer isconstructed. It is believed that fabrics having continuous fibers orfibers melted together can appear to have lower resistance with greatercontinuity of the metallic layer. It is thought that the larger thesurface area of fiber contact, the better the conductivity and the lowerthe resistance. It is also believed that the polymeric foam materialsthat are autocatalyticly metal plated provide a large surface area ofmetallic silver with low resistance and high conductivity.

A preferred aspect of the conductive layer is a non-conductive polymericfilament/fiber substrate that has been autocatalytically plated withsilver. FIG. 7A is a representative cross-section of a polymericautocatalytically plated fabric composed of multifilaments formed intoyarns and knitted into a fabric. FIG. 21 represents a multilobular fiberthat is uniformly metal plated on all surfaces. All filaments, (40) arethree dimensionally coated with a uniform layer of metal (41). FIG. 7Brepresents a cross-section enlarged detail of FIG. 7A showing theuniform metallic coating (41) of one filament (40).

FIG. 7C is an enlarged detail of FIG. 7B showing the uniformity ofmetallic plating covering the polymeric substrate. FIG. 7D is anenlargement of the metallic surface of a polymeric autocatalyticallyplated filament representing approximately 62 μm² of surface area.

Another preferred aspect of the conductive layer is a non-conductivepolymeric foam substrate that has been autocatalytically plated withsilver. FIG. 19 and FIG. 20 are representative cross-sections of apolymeric autocatalytically plated foam. FIG. 19 represents a polymericfoam substrate (151) with a second polymeric foam coating (152) that isin turn autocatalytically metal plated (153). FIG. 20 represents apolymeric foam substrate (160) that is autocatalytically metal plated(161). Open spaces are represented in FIG. 19 and FIG. 20 by 162 and154. All metal plated surfaces are three dimensionally coated with asubstantially uniform layer of metal.

FIGS. 7A, 7B, 7C and 7D demonstrate that the actual surface area ofmetallic silver exposed to a liquid can be significantly greater thanthe geometric surface area of the fabric. Assuming the surface of theplated metal is smooth, the ratio of geometric surface area to actualsurface area can have a range from about 1:2 to about 1:10,000, fromabout 1:10 to about 1:1000, from about 1:10 to about 1:500, 1:20 toabout 1:500, from about 1:20 to about 1:250, from about 1:10 to about1:250, from about 1:10 to about 100 and an optimal ratio range fromabout 1:20 to about 1:100. Taking into consideration FIG. 3D, it isbelieved that the actual surface area can be extended by a multiple ofbetween about 10 and about 1000 above the calculated smooth surfacearea. Even though a uniform coating is preferred, there may beapplications wherein non-uniform coatings are preferable.

The thickness of the uniform coating can vary from about 0.1 micrometersto about 2.0 microns, from about 0.1 microns to about 1 micron, fromabout 0.1 microns to about 1.5 microns, preferably from about 0.2microns to about 1.5 microns. Preferably, the thickness of metal coatingis directly correlated with the percentage of weight of silver plated tothe weight of the fabric without silver plating. The amount of coatingcan vary from about 5% to about 40% by weight, from about 5% to about30% by weight, from about 5% to about 20% by weight, from about 5% toabout 10% by weight, from about 10% to about 30% by weight, from about10% to about 25% by weight, from about 10% to about 20% by weight, fromabout 15% to about 30% by weight, more preferably between about 15% toabout 22% by weight. While not wishing to be bound to any particulartheory, it is believed that filaments and fibers that are uniformlyplated may have the greatest electrical conductance and the lowestelectrical resistance. Preferably, the maximum conductance and minimumresistance can be directly correlated. Preferable for the disclosure isa plating thickness between about 0.2 to about 1.5 microns, and betweenabout 14% to about 22% of the weight of the plated fabric composed ofmetallic silver. Most preferably, the conductivity of the plated fibercan significantly decrease when the percent of weight of plated fabricfalls below about 10%. Silver-coated fibers suitable for use in thepresent disclosure are commercially available.

The dressings can also comprise at least one absorbent layer (116) thatfunctions primarily as a reservoir for donating, receiving, or storingwound exudates or other fluids.

The absorbent layer may provide a source of moisture in wounds withminimal fluid drainage or □bsorben by receiving and holding fluids thatare provided from an external source through a plurality of apertures inlayers superficial to the absorbent layer. The absorbent layer maycontain any number of layers of conductive metal plated fibers uniformlymixed with non-conductive fibers. The absorbent layer can also compriseonly non-conductive fibers or material. For purposes of the disclosure,non-conductive fibers or material are any fibers or materials that arenot coated with a metal or metal alloy and are not capable of conductingan electrical charge or releasing ions.

The at least one absorbent layer can comprise any absorbent material,and the dressing can comprise any number of absorbent layers positionedadjacent to any other layer of the dressing. Advantageously, theabsorbent layer can be positioned adjacent to the moisture regulationlayer. In another aspect of the disclosure, the absorbent layer can bepositioned between the conductive layer and the moisture regulationlayer.

Absorbent materials suitable for the absorbent layer comprise anybiocompatible synthetic or natural absorbent material known in the artincluding, but not limited to, a foam, a sponge or sponge-like material,cellulosic materials, cotton, rayon, polyvinyl alcohol, polyvinylacetate, polyethylene oxide, polyvinyl pyrrolidon, polyurethanehydrocolloids, alginates, hydrogels, hydrocolloids, hydrofibrils,collagens or any combinations thereof.

In one aspect of the absorbent layer, layers of metal plated conductivefibers and non-conductive fibers can be uniformly distributed throughoutat least one or more layers. Alternatively, metal or metal alloy platedand non-conductive fibers can be uniformly distributed throughout theabsorbent layer. It is contemplated as being within the scope of thepresent disclosure to have layers of absorbent material of differingratios of metal plated conductive fibers to non-conductive fibers aswell as differing thicknesses of the layers. The layers may be in theform of woven, knitted or non-woven fabrics. The absorbent layer (130)demonstrated in FIG. 14 is composed of layers (131, 132, and 133) of theabsorbent material with varying ratios of metal plated conductive fibersto non-conductive fibers and varying layer thicknesses. As theconcentration of metal plated conductive fibers increases and theconcentration of non-conductive fibers decreases, the ratio of metalplated conductive fibers to non-conductive fiber increases. As theconcentration of metal plated conductive fibers decreases and theconcentration of non-conductive fibers increases, the ratio of metalplated conductive fibers to non-conductive fibers decreases. In a givenlayer, the ratio of metal or metal alloy plated conductive fibers tonon-conductive fibers can be from about 1:100 to about 1:0, from about1:75 to about 1:0, from about 1:60 to about 1:0, preferably from about1:50 to about 1:0, from about 1:40 to about 1:0. from about 1:30 toabout 1:0 and more preferably from about 1:25 to about 1:0. In thesituation wherein the layers comprise about 100% conductive metalfibers, the ratio would be about 1:0. The ratio of conductive metal ormetal alloy plated fibers to non-conductive fibers, although constantwithin a given layer, may vary from layer to layer.

Advantageously, there can be an increasing ratio of conductive metalplated fibers to non-conductive fibers the closer the layer is to thewound. Thus, there can be a decreasing concentration gradient ofconductive metal fibers in each subsequent layer further from the woundsite. Concentration gradients of mixed fibers can be made according toprocesses known to those of ordinary skill in the art.

The thickness of layers (131, 132 and 133) of FIG. 10 may be similar ormay vary. Ideally, the thickness of the layers increases as the distancefrom the wound surface increases. In an additional preferred aspect, theincreasing thickness of the layers occurs in a ratio of the absorbentnumbers (i.e., 1,2, 3,5, 8, 13, 21 . . . ).

In another aspect of the absorbent layer, shown in FIG. 16, a multilayerstructure (140) comprises conductive layers (141, 142, 143), with anon-conductive layer (144) interposed between conductive layers (141)and (142), and a non-conductive layer (145) interposed betweenconductive layers (142) and (143). The composition of conductive layersmay be similar and formed from conductive metal plated fibers or amixture of conductive metal or metal alloy plated fibers andnon-conductive fibers in the form of a woven, knitted or non-wovenfabric. The mixture of conductive metal or metal alloy plated fibers andnon-conductive fibers can be uniform in each layer and may have adecreasing ratio of conductive plated metal fibers to non-conductivefibers the closer the layer is to the wound surface. A layer ofnon-conducting, flexible material can be positioned between theconductive layers. In one aspect, the non-conductive layers can becomposed of impermeable or semi-permeable materials with aperturesdisposed substantially throughout.

In FIG. 16, the use of the alternating conductive metal plated fiberlayers (141, 142 and 143) and non-conductive fiber layers (144 and 145)can create a capacitor-like laminate.

The moisture regulation layer (118) shown in FIG. 11, can be anybiocompatible semi-permeable or impermeable material for limiting theevaporation of moisture from the absorbent layer and the wound surface.At least one moisture regulation layer (118) can be positioned adjacentto the conductive layer or adjacent to the absorbent layer of thedressing. Advantageously, the moisture regulation layer can bepositioned adjacent to the absorbent layer and can be fixedly attachedor removably attached for easy removal and replacement.

The moisture regulation layer not only controls the rate of moistureevaporation from the absorbent layer, but also functions as a physicalbarrier to the penetration of microbes from the surrounding environment.The rate of moisture evaporation from the moisture regulation layer isrelated to the size of the apertures. Very small aperture sizes allowthe release of gases but not liquids, while larger aperture sizes allowthe release of gases and liquids. Even larger-sized apertures allow theentry microbes such as bacteria and fungi and environmentalcontaminants. Though not wanting to be bound by any particular theory,it is theorized that the placement of apertures larger than the size ofmicrobes (such as bacteria and fungi) in this layer runs counter to theprevailing teaching that a physical barrier must be provided to preventthe penetration of microbes from the surrounding environment. Someembodiments substitute the traditional physical anti-microbial barrierto microbial penetration with a functional anti-microbial barrierthrough application of the anti-microbial metal plated fibers. Thefunctional anti-microbial barrier of anti-microbial metal plated fibershas allowed the apertures to be placed in the moisture regulation layerwithout fear of compromise of the physical barrier to environmentalmicrobial contamination of the wound.

The moisture regulation layer can be a film, fabric or foam. Somepreferred materials include, but are not limited to, polyurethanes,polyolefins such as linear low density polyethylene, low densitypolyethylene, ethylene vinyl acetate, vinylidene, chloride copolymer ofvinyl chloride, methyl acrylate or methyl methacrylate copolymers andcombinations thereof. A preferred polymeric material is polyurethane,either as a film or as a polyurethane foam. The polyurethane may be anester or ether based polyurethane.

Materials suitable for a foam moisture regulation layer can be anysemi-permeable or impermeable natural or synthetic compound including,but not limited to, rubber, silicon, polyurethane, polyethylenepolyvinyl, polyolefin, silicone or combinations thereof.

Alternatively, the moisture regulation layer, (118), may be atransparent elastomer film for visual inspection of the moisture statusof the absorbent layer dressing.

Preferably, the film can have a thickness from about 10 μm to about 100μn, from about 10 μm to about 90 μm, from about 10 μm to about 80 μm,from about 15 μm to about 100 μm, from about 15 μm to about 90 μm, fromabout 15 μm to about 80 μm, from about 15 μm to about 70 μm, from about20 μm to about 100 μm, from about 20 μm to about 90 μm, and morepreferably from about 20 μm to about 80 μm. In some materials, athickness below 10 μm may result in poor mechanical strength or handlingproperties and a thickness of the transparent elastomer film exceedingabout 100 μm may result in poor flexibility and comfort to the body.Preferably, the moisture regulation layer has an MVTR of from about 300to about 5,000 grams/meter/24 hours, preferably from about 800 to about2,000 grams/meter/24 hours. The moisture regulation layer can belaminated to the absorbent layer by methods well recognized in the art.

To regulate the moisture level of the wound dressing, apertures, (111)as illustrated in FIGS. 10A and 10B, are disposed in the moistureregulation layer. The apertures can be any geometric shape having curvedlines, straight lines, or a combination thereof.

Shapes include, but are not limited to, slits, stars, oval, circles,semicircles, squares, rectangles, polygons or any combination thereof.The apertures can be disposed randomly or in uniform patterns, groups,or bunches. Such apertures allow for addition or removal of liquids fromthe absorbent layer. In a method of use for wound treatment, theapertures would allow the wound to be bathed by dispensing liquids,medicaments, cleansing or treating agents, without removing thedressing.

The size of the apertures can improve the regulation of the moisturelevel of the absorbent layer, the conductive layer, and the surface ofthe wound. It is believed that the regulation of the moisture level inthe wound provides benefits such as the release of anti-microbialmetallic ions from the conductive metal plated fibers and fabrics andenhances the analgesic effect, improves conductivity of the conductivemetal plated fibers, and assists with restoration of the electricalpotential of the wound site. As a result, while not wising to be boundto any particular theory, it is believed that the cellular growth andregeneration is enhanced, expediting the healing of the wound.

Large apertures in general can cut through one layer or multiple layers.The apertures are positioned to allow direct liquid and medicants to beadministered from the external environment to the absorbent layer. Theapertures (111) of the multilaminate wound layer dressing (110) of FIGS.7 and 14 are cut through the moisture regulation layer and are not cutthrough the absorbent layer or other layers between the moistureregulation layer and the surface of the wound. The apertures (111) ofthe multilaminate island wound dressings, (120) of FIG. 13 and FIG. 17(150), are cut through the backing sheet, the adhesive layer, and themoisture regulation layer. With respect to the island wound dressing,(120) of FIG. 13, the aperture pattern is limited to the area over themoisture regulation layer. The apertures in the island dressing of FIG.13 extend through a back sheet layer (112), adhesive layer (119) andmoisture regulation layer (118).

Advantageously, a semipermeable or impermeable moisture regulation layercan be laminated to an absorbent layer such that, regardless of thepattern of apertures, delamination of the moisture regulation layer fromthe absorbent layer does not occur. The apertures allow for movement offluids or medicants to and from the absorbent layer. The regulation ofmoisture content can be controlled by application of fluids via a bulbsyringe or similar application device, or alternatively by a secondarydressing (120) as shown in FIG. 18.

In alternative aspects of the disclosure, it is helpful to provide amoisture regulation layer that is releasably or removably attached to anabsorbent layer or a conductive layer of the dressing. This allows forthe removal and replacement of the moisture regulation layer withoutdisturbing the wound. The moisture regulation layer can be affixed tothe adjacent layer by any artful means that will allow for quick removalfrom the absorbent layer including, but not limited to, adhesives,knitting techniques, lamination, or a combination thereof.

The layers of the devices of the present disclosure may or may not beattached to each other or be provided as a component of anotherstructure. For example, a metallic, conductive layer, made frommetal-plated fibers, is applied directly to the affected site, such as awound. A foam is then applied as a second layer above the site toprovide the □bsorbent layer. A moisture retention layer is then placedon the surface of the foam farthest from the affected site to controlthe moisture content of the affected site. In another example, a two orthree layer bandage, comprising at least a conductive layer as the firstor second layer closest to the affected site, is provided wherein thelayers are attached to one another.

In any aspect of the present disclosure, the conductive layer can bepositioned in the dressing for placing in direct contact with the woundsurface upon application of the dressing to the wound. Alternatively,the absorbent layer can be positioned in the dressing for placing indirect contact with the wound surface upon application of the dressingto the wound. For treatment of internal wounds, for example for treatingsurgical wounds on internal organs, the conductive layer or absorbentlayer can also be positioned for placement in direct contact with thewound surface upon application of the dressing to the wound.

The disclosed wound dressings can also have the conductive layer iscoated with a conductive coating for example, a hydrogel, and optionallywith a calcium alginate.

The various aspects of the wound dressings of the disclosure cancomprise an optional adhesive layer positioned between any adjacentlayers, or advantageously, the adhesive layer can be the top layer ofthe dressing. Useful adhesives include those known in the wound dressingart, including but not limited to, rubber-based, acrylic, vinyl etherand hydrocolloid pressure sensitive adhesives. Conveniently,anti-microbial agents can be added to the adhesive material.

The disclosed devices can be formed into any of a number of possibleshapes, patterns orgeometrics, depending upon the application andtopography of the wound or application site. Any aspect of the wounddressing of the present disclosure can be manufactured in a variety ofshapes and configurations. For example, configurations can include, butare not limited to, compressive wraps, tampons, tubular, roll gauze,pads of varying sizes and shapes, island dressings, strip dressings,dressings for dental applications, rectal dressings, vaginal pads,surgical packing or dressings, or any combination thereof.

FIG. 15 shows a tubular configuration of the wound dressing. The tubularconfiguration may be composed of one or more layers. The layers can becomposed of about 100% metal plated fibers or foam or a ratio ofconductive metal fibers or foam to non-conductive fibers or foam. Thetubular configuration can take the shape of a wrap for circumferentiallyplacing around an area to be treated. The distribution of conductivemetal fibers and non-conductive fibers in each layer can be uniform. Theconductive metal plated fibers of layers 131 a, 132 b and 133 crepresent an increasing ratio of conductive metal plated fibers tonon-conductive fibers as the layers are positioned closer to the woundcontact surface. The layers can be in the form of a woven, knitted ornon-woven fabric. The tubular configuration of this aspect of thedisclosure can be used in dressing applications including, but notlimited to, a vaginal, mouth, nasal, external ear canal, or rectal areadressing.

Another wound dressing configuration is the island dressing. FIGS. 12,13 and 17 demonstrate various representative aspects of islanddressings. FIG. 12 shows the top view of a dressing with placement ofthe apertures (111) over the conducting layer (114), the absorbent layer(116), and the moisture regulation layer (118) but not in the peripheralarea of an adhesive layer. A cross-section of FIG. 12 is shown in FIG.13. A release liner layer (117) extends the entire surface of anadhesive layer (119) on the moisture regulation layer (118). The releaseliner layer is removed prior to application of the island dressing to awound surface. An adhesive layer (119) is laminated to a backing sheet(112), and may include pressure sensitive adhesives for securing thedressing over the wound.

FIG. 17 illustrates an example of a multi-layer wound dressing in anisland configuration, (150) having the same laminar composition as thedressing (120) shown in FIG. 13, with the exception that conductivelayer (125) has been added between the absorbent layer (126), and themoisture regulation layer (128). The conductive layer (125) has similarcomposition to conductive layer (124). Both can be composed of about100% conductive metal plated fibers, woven, knitted or non woven. Themoisture regulation layer (128) can be adjacent to a backing sheet(122), that can be coated with a pressure sensitive or heat sensitiveadhesive (129) on the surface that is facing the moisture regulationlayer (128). The moisture regulation layer, both conductive layers, andthe absorbent layer all have the same length and width, and aresubstantially of smaller dimensions than the backing sheet (122) andpressure sensitive adhesive layer (129). They are also centrally seatedon the adhesive surface (129) and the backing sheet (122), leaving anedge of the adhesive layer exposed around the perimeter of the layers,thus providing an island dressing configuration adapted for securing thedressing to the skin. Apertures penetrate through the backing sheet(122), the adhesive layer (129), and the moisture regulation layer (128)over the area covered by the moisture regulation layer, both conductivelayers and the absorbent layer. A release liner layer (127) covers theentire perimeter of the adhesive layer (129) prior to use, in order toprevent premature, unwanted contact of the adhesive-bearing surface.

In another aspect of the disclosure, a secondary dressing (160),illustrated in FIG. 18, may be applied to any aspect of the disclosedwound dressings (110, 120, 130, and 150). The secondary dressingprovides a source for liquids and medicants that can be added to thewound dressings in addition to, or in combination with, the manualapplication of fluids or medicants using devices such as a bulb syringe.The secondary dressing (160) is composed of a pressure adhesive layer(142), an absorbent layer (141) and a semipermeable backing layer (143).The dimensions of the secondary dressing correspond to the dimensions ofthe wound dressing.

The pressure sensitive adhesive layer (142) is continuous around theperimeter of the secondary dressing. The pressure sensitive adhesivelayer secures the secondary dressing to the primary dressing over thearea of the apertures. The secondary dressing can be easily changed andremoved on an as-needed basis without disturbing the healing of thewound. The adhesive may be any of the medical grade adhesives heretoforeemployed for application to the skin. The absorbent layer (141) maycontain a mixture of conductive metal plated fibers and non-conductivefibers, all conductive metal fibers, or all non-conductive fibers. Themoisture regulation layer (143) can be an impermeable synthetic film.

The secondary dressing may be releasably secured to the primarydressing, such that the secondary dressing may be removed and replacedwithout removing or disturbing the primary wound contact dressing, forexample, when the secondary dressing becomes saturated with woundexudates. The secondary dressing can be designed for the removal ofexcessive wound exudates or for the addition of liquids and medicants.

In another aspect of the disclosure, a fabric comprising any of thevarious aspects having conductive layer, absorption layer and moistureregulation layer of the disclosed device, can be provided. Afterassembly of the layers, the layers are laminated into a fabric suitablefor cutting and forming into various configurations of wound dressingsor wound healing devices.

Embodiments of the disclosure comprise wound dressings or devices,comprising, at least one conductive layer. The wound dressing canfurther comprise at least one absorbent layer or at least one moistureregulation layer comprising a plurality of apertures disposed in themoisture regulation layer or any combination of the layers. Apertures ofthe moisture regulation layer allow passage of materials ranging in sizefrom no passage of materials, that is moisture regulation layers with noapertures, apertures that allow gases but not liquids to pass, toapertures that allow liquids and gases to pass, to apertures of a sizesufficient for the passage of microbial or environmental contaminants.The dressings may comprise moisture regulation layers attached to atleast one absorbent layer or at least one conductive layer. Theconductive layer may comprise at least one fiber that is coated threedimensionally with a metal or a metal alloy. The metal is selected fromcopper, silver, gold, palladium, nickel, cobalt or a combination thereofor the metal is selected from an alloy of nickel and boron, cobalt andboron, palladium and boron, nickel and phosphorus, cobalt andphosphorus, palladium and phosphorus, or a combination thereof. Theconductive layer may also comprise a polymeric foam coated threedimensionally with metal or a metal alloy. The conductive layer maycomprise at least one fiber or foam having grooves or channels along thelongitudinal axis of the fiber or foam for capillary movement of water,to store or trap substances, and to provide large active surface areasfor a given denier per fiber or foam.

Certain embodiments of the disclosed devices have at least oneconductive layer comprising at least one conductive fiber comprising athree dimensional coating of a metal, and at least one non-conductivefiber, wherein the conductive fiber and nonconductive fiber areuniformly distributed throughout the layer. The nonconductive fibers canbe composed of natural polymers, synthetic polymers, alginates,chitosan, rayon, cotton, or other polymeric substrates. Polyurethane isa preferable material for conductive and nonconductive fibers and foams.Absorbent layers can comprise a plurality of layers wherein the ratio ofconductive fibers to non-conductive fibers is constant in a given layeror varies from layer to layer. In an embodiment, the ratio of conductivefibers to nonconductive fibers increases as the absorbent layer ispositioned in closer proximity to the wound. Alternatively, theabsorbent layer comprises conductive fibers comprising a threedimensional coating of a metal, and non-conductive fibers, wherein theconductive fibers and nonconductive fibers are uniformly distributedthroughout the layer. The same arrangement of fibers and foams can befound in embodiments of conductive layers. In the layers, the ratio ofconductive fiber to non-conductive fiber is between about 1:100 to 1:0,or the ratio of conductive fiber to non-conductive fiber is betweenabout 1:50 to 1:0, or the ratio of conductive fiber to non-conductivefiber is between about 1:25 to 1:0.

Still other embodiments may comprise a magnetic field provided to thewound surface by the conductive layer. A dressing may further comprisean adhesive layer.

The conductive layer may comprises a fiber or foam three dimensionallycoated with a metal.

The at least one moisture regulation layer may be positioned adjacent toat least one absorbent layer. The layers may be shaped as polymericsheets, films, or foams. An embodiment of a dressing may have multiplelayers of conductive and absorbent layers. The at least one absorbentlayer may comprise a plurality of layers, each layer increasing inthickness as the proximity from the wound increases. Embodiments includedressings where the conductive layers and absorbent layers alternate.The dressings may be formed into a shape selected from a pad, a tampon,a tubular configuration, an island dressing, a strip dressing, or anycombination thereof. The apertures of the dressings may a geometricshape having curved lines, straight lines, or a combination thereof.

In treatment of wounds and use of the dressings described herein, asecondary dressing may also be used. A secondary dressing for applyingto a wound dressing comprising at least one absorbent layer, at leastone semi-permeable backing layer and a pressure adhesive layercontinuous around the perimeter of the backing layer. These and othersimilar embodiments are intended by the present disclosure.

Certain embodiments of the disclosed devices are advantageous over theprior art because they do not require an external energy source orgalvanic cell action to create and deliver silver ions. Wound dressingscan be formed into a number of different useful forms, depending on theparticular application. In addition, the proper moisture environment atthe treatment site can be created and regulated by controlling theamount of fluid at the wound site without disturbing the wound.

Methods of Use

Healthy human skin exhibits an electrical potential across theepithelium that is referred to as the transepithelial potential (TEP) orepidermal battery. The TEP is generated by an active ionic transfersystem of sodium ions that enter the outer cells of the epithelium viaspecific channels in the outer membrane of these cells and migrate alonga steep electrochemical gradient. The epidermal battery is generatedthrough a series of electrogenic pumps that actively pump sodium ions,and tight gap junctions between epithelial cells that do not allow thereverse passage of the sodium ions. This results in the transport ofsodium ions from the water bathing the epithelium cells to the internalbody fluids of the animal, and causes the generation of a potential onthe order of −10 mV to −70 mV across the epithelium.

It is believed that when a wound is made in the skin, an electric leakis produced that short-circuits the TEP allowing the voltage to reverseat the wound surface.

With the disruption of the epithelium's electrogenic sodium transportmechanism within the wound, the TEP on the surface of the wound issignificantly altered in the reverse direction. As one progresseslaterally from the wound surface to normal tissue surrounding the wound,the potential across the skin increases, until a point is reached atwhich the potential across the skin is the full value normally found inunwounded skin. Thus a lateral voltage gradient is generated in theproximity of the wound margin as one transitions from wounded tissue tonormal tissue. Various studies have reported that the lateral voltagegradient in experimental animals could be as high as 140 mV/mm. It hasalso been reported that within 24 hours after a wound is formed, theepidermally generated lateral voltage drops by 95%. Therefore, it isrecognized that there is a lateral voltage gradient or “lateralpotential” in the epidermis close to the margin of a wound. The greatestepidermally generated lateral voltage is found in the region of highesttissue resistance. In the amphibian, the locus of the major lateralpotential is at the high resistance space between the epidermis and thedermis. In the mammal, the locus of the major lateral potential is atthe space between the living and the dead cornified layers ofepithelium.

While not wishing to be bound to any particular theory, the role of TEPin wound healing is explained in reference to FIG. 5 which demonstratesa cross-sectional representation of typical mammalian skin (5) with anelectrical circuit generated by the TEP overlayed on the skin anatomy.The epidermis (7) overlies the dermis (9) at junction (11) and includesthe stratum corneum layer (13) and the stratum spinosum layer (15) witha junction (17) there between. The stratum corneum layer is composed ofdead cornified squamous epithelium. The wound (19) is filled with bothcellular and dissolved elements of the blood including fibrinogen,fibronectin, polymorphonuclear leukocytes, platelets and red bloodcells. Depending upon the location on the body (24) the surface (21) ofthe skin distal to the wound (19) can be expected to have a potential ina range of from about −10 to about −70 millivolts due to the TEP. Theresistance of the return paths of current that is induced by aphenomenon known as an epidermal battery (29) is represented byresistors (25). The resistance of the wound is represented at (27). Adressing (120) in accordance with the present disclosure and having ahighly conductive layer (114), absorbent layer (116), semipermeablelayer (118), adhesive layer (119) and backing sheet layer (112), isshown proximate to the wounded skin surface (21). Prior to placement ofthe dressing on the wound, the wound potential (23) is more positivethan on the surface of the skin (21), utilizing the surface potential tobecome less negative and, in certain instances, become positive. Whilenot wishing to be bound to any particular theory, it is believed thatthis is due to the removal of the epidermal battery (29) at the wound(19). The further the potential test point (23) is from the unwoundedsurface (21), the more closely the potential will approximate thepotential of the positive side of the battery (29). If the wound is wetand therefore conductive, a wound current between points (31) and (33)will be induced by the TEP. The wound current will pass through theexudates and debris filling the wound (19) along the most efficient orlowest resistance path available. This is most likely proximate to theedge of the wound, because this will be the shortest path and the mostmoist path available. The wound current will pass from point (31)through the resistance at the junction (11) represented by resistor(35), into the wound at point (37), through the wound resistance (27) topoint (39), where it re-enters the epidermis (7) at the junction (17),through the resistance of junction (17), represented as resistor (25),to point (33) on the other side of epidermal battery (29).

While not wishing to be bound by any particular theory, it is believedthat when the dressing (120) is placed on the wound (19), the conductivelayer (114) lowers the electrical potential of the wound, (e.g., at 23)by virtue of electrical contact with uninjured skin surfaces (21) whichhave a negative potential established by the epidermal battery (29).Certain embodiments of the disclosed devices can reduce the woundpotential or make the wound potential more negative by about 1 mV, about5 mV, about 10 mV, about 20 mV, about 30 mV, about 40 mV, about 50 mV ormore. Still other embodiments can reduce the wound potential by about0.1 mV to about 20 mV, typically from about 1 mV to about 10 mV. It willbe appreciated that the term reducing the wound potential refers tomaking the wound potential more negative.

The dressing (120) lowers the potential of the wound surface andprovides a conductive bridge between healthy skin surfaces (21) oneither side of the wound (19). The point of maximum resistance shiftsfrom point (39) to point (37). This in turn shifts the point of maximumlateral potential drop from point (39) to point (37). With the shift inlateral potential, the electrical characteristics of the wound moreclosely resemble the amphibian wound than the mammalian wound. Amphibianwounds are known to heal significantly faster than mammalian woundsbecause of this shift. Wound healing is enhanced and accelerated by theshift caused by the highly conductive surface of the wound dressing ofthe present disclosure. The shift in lateral potential from point (39)to point (37) can reduce the amount of stimulation that superficialnerve endings receive, thereby aiding in creating an analgesic effect,an anti inflammatory effect, or a combination thereof. It is believedthat the moisture level of the dressing (120) augments the restorationof the negative TEP and assists with the shift in lateral potential todeeper structures.

FIG. 7 is a representative graph of the voltage at the surface of humanskin as one proceeds from normal skin (21) to the open wound (23) tonormal skin again. The area of normal skin (21) measures a relativelyconstant negative voltage between about 10 and about 70 millivolts. Itis believed that the area of the wound surface where the TEP and theepidermal battery are disrupted (23) is always more positive thanuninjured skin (21), reaching voltages between (23′) and (23). When adressing (110) in accordance with the present disclosure is applied andthe wound is kept moist, it is possible to return to more normal skinpotentials as shown at (21′).

It is believed that the dressings of the present disclosure cancontribute to expedited healing of the wound and aid in providing relieffrom the pain associated with wounds. Without wishing to be bound by anyparticular theory, the principle mechanisms of action that may accountfor the pain relieving aspects of the dressing of the present disclosurecan be derived from the conductive layers of the dressing. First, thesilver can create an antibacterial environment, which in turn candiminish the inflammation caused by the bacteria and subsequently candiminish pain. And second, the effect of a highly conductive layer canhave a positive effect on the electrical field environment of the woundto be healed.

The present disclosure comprises methods of treating a wound in a humanor an animal comprising, a) applying a dressing to a wound on a human oranimal wherein the dressing comprises at least one conductive layer;optionally at least one absorbent layer; and optionally, at least onemoisture regulation layer comprising a plurality of apertures disposedin the moisture regulation layer; b) monitoring the absorbent layer ofthe dressing to determine a variation from a predetermined fluid level;and c) adding or removing fluid through the moisture regulation layer tomaintain the predetermined fluid level. Methods can further compriseaffixing a secondary dressing to the external surface of the dressingapplied in step a) to the wound, wherein the optional secondary dressingcomprises at least one absorbent layer, at least one semi-permeablebacking layer and a pressure adhesive layer continuous around theperimeter of the backing layer.

In another aspect of the disclosure, the wound dressings can be used toregulate the moisture level of a wound of a human or animal. Manydressings are available that attempt to control the moisture level ofwounds. Moisture retention is a term that refers to the ability of adressing to consistently retain moisture at the wound site byinterfering with the natural loss of moisture vapor due to evaporation.Semi-occulsive and occlusive wound dressings, such as films, foams,hydrogels and hydrocolloids, can be used to keep a wound moist bycatching and retaining moisture vapor that is being lost by the wound.Normal skin has a moisture vapor transfer rate (MVTR), also called atransdermal water loss (TWL), of 43.2 grams/meter/24 hours. Many filmdressings have MVTRs ranging from 400 to 2000 grams/meter/24 hours.Superficial wounds such as tape-stripped skin have an initial MVTR of7,874 grams/meter/24 hours. In general, if a dressing material transmitsless moisture vapor than the wound loses, then the wound will remainmoist. When wound drainage levels are high, simple transmission of vaporwill not dissipate adequate moisture to maintain physiologic tissuehydration. If the moisture vapor transmitted by a dressing issignificantly less than the moisture being lost by the wound in vaporand liquid form, then drainage accumulates and remains in contact withthe wound and surrounding skin. To maintain high drainage levels, adressing must also have a liquid absorptive capacity in addition tovapor transmission ability. The process of absorption physically movesdrainage away from the wound's surface and edges and into the dressingmaterial. At the other end of the hydration spectrum, wound tissue thatis already dry may need to be actively re-hydrated using dressingmaterials that donate water to the tissue or by removing the dressingand manually applying fluids to the wound.

One of the embodiments of the present disclosure allows for the additionor removal of fluid from the wound without removing the dressing. Thiscontrol of fluid can be extremely important in trauma or battlefieldsituations where fluids need to be provided quickly. Additionally, thepresence of the metal ions, provided by the conductive fibers or foams,aids in control of microbial contamination and thus, non-sterile fluidscan be used.

The moisture level of the wound can be regulated in comparison to somepre-determined level of moisture that can be beneficial. Advantageously,an indicator can be added to the wound dressing to indicate moisturelevel, electrical potential, metallic ion concentration, or pH.

To treat wounds, of an animal or human, the appropriate aspect of thewound dressing is selected and positioned on the wound, with theconductive layer in contact with the wound. The absorbent layer of thedressing is observed for variation of a moisture level that has beenpredetermined to be advantageous. Moisture, fluids, and medicants can beadded to the wound dressing as needed through the moisture regulationlayer. Moisture in excess of the predetermined level can also be removedthrough the moisture regulation layer.

Alternatively, the moisture regulation layer can be removed and replacedwith a new moisture regulation layer without disturbing the healingwound. Means to add and remove moisture include, but are not limited to,sponges, suction bulbs, negative pressure inducing devices or vacuums,syringes, gauze pads and the like.

In another aspect of the disclosure, a secondary dressing comprising atleast one absorbent layer, at least one semi-permeable backing layer,and a pressure adhesion layer can be affixed to the external surface ofthe wound dressing. The secondary dressing can comprise liquids and/ormedicants for treating the wound. The secondary dressing can be removedand replaced as needed to encourage continued healing of the wound.

In another aspect of the disclosure, the wound dressing can be placedinternally to treat an organ or internal surgical incision. The dressingcan be in the form of a gauze pad, packing material, fibrous dam, or anymeans to convey the treatment of the wound.

The wound dressing, when saturated and overlapping normal skin, mayallow for controlled maceration of the surrounding uninjured skin. It iscurrently believed that the maceration of normal skin should be avoided.Maceration of normal skin is known to cause a breakdown of the cornifiedepithelium with subsequent loss of the anti-microbial barrier functionof the skin. The reduction of the anti-microbial barrier function of thecornified epithelium is believed to result in an increased risk ofmicrobial contamination at the wound surface. In an effort to controland prevent skin maceration, wound dressing designers have constructedwound dressings with special features that reduce the occurrence ofmaceration.

Without wishing to be bound, it has unexpectedly been determined thatthe occurrence of maceration of normal skin surrounding a wound underthe wound dressing of the present disclosure has not resulted inincreased bioburden and/or contamination of the wound surface. While notwishing to be bound to any particular theory, the present disclosure hasdetermined that the maceration of normal skin surrounding a wound beingtreated by the present disclosure has altered the local electrodynamiccharacteristics and resulted in an enhancement of the wound healingprocess.

It has been observed that regulating the moisture in and around themetal-plated fibers of the wound dressings of the present disclosure mayfacilitate the release of metallic ions from the surface of the metalbecause the passive release of metal ions can only take place within aliquid medium. Therefore, it is advantageous to keep the wound dressingmoist in order to provide the effect of the metal plated fibers. Woundsthat generate fluid exudates will usually provide the needed moisturerequired to activate the release of metal ions from the metallicsurface.

Methods of Making

The preferred method of plating a metal on a fiber or foam for theconductive layer of the present disclosure is autocatalytically platingbecause it coats the fiber or foam uniformly with a three dimensionalcoating. This provides the maximum available surface area for accessiblemetal ions. In general, the fiber or foam has a nitrogen group. If thematerial from which the fiber or foam is made does not provide anitrogen group on the surface, such nitrogens can be provided by added alayer of material or a coating that provides a nitrogen group on thesurface. The present disclosure comprises use of materials that can besensitized for autocatalytic metal plating. Such materials can be madeinto fibers, foams, films or other structures that function to providethe wound healing attributes of the devices described herein. Forexample, such materials include, but are not limited to, materialshaving nitrogen or silicon dioxide or other equivalently functionalgroups, that are capable of being sensitized. With, for example, thenitrogen group or silicon dioxide on the surface, the material can thenbe sensitized using methods known in the art. Once the material issensitized, autocatalytic metal plating or coating of the material isperformed.

The principle benefits of autocatalytically metal plating are: (1)uniform circumferential, three dimensional metal plating of thefilament, foam, fiber, yarn or fabric; (2) large ratio of total metalsurface area to geometric surface area; (3) high conductivity and lowsurface resistivity of the plated filaments, fibers, yarns and fabrics;(4) excellent adherence of the metallic coating to the non-conductingpolymeric substrate with reduced risk of the metal coating flaking orfracturing off the non-conducting substrate; (5) excellent flexibility,conformability and elastomeric qualities; and (6) no limitations onfilament, fiber, yarn or fabric design and construction.

Autocatalytic plating describes the method of depositing metals or metalalloys on non-conductive substrates by means of reduction-oxidationchemical reactions. Unlike electroplating, autocatalytic plating doesnot apply an electrical current from an external source to a conductivematerial or substrate for the purpose of depositing metals on thesurface of the substrate. If the substrate is non-conductive,electroplating is not possible.

Pure metal elements such as copper, gold, nickel and silver as well asbinary alloys of nickel, cobalt or palladium with phosphorus or boroncan be plated onto non-conductive material or substrate by theautocatalytic plating process.

The autocatalytic plating baths are designed such that when a sensitizedsubstrate is introduced into the plating bath, deposition of the metalbegins in a slow and uniform manner on all surfaces of the substrate.Once the process is initiated, the plating solution will continue toplate because the deposited metal catalyzes its own plating, thus makingthe reaction autocatalytic.

The autocatalytic metal plating process is the plating process of choicefor filaments, fibers, yarns and fabrics in the electro-staticdischarge, electromagnetic interference and radio frequency interferenceindustries. Autocatalytic metal plating of non-conductive substrates isused because the process is known to be superior to the vacuum vapordeposition process, the sputter coating deposition process, includingmagnetron sputtering, and the ion-beam assisted deposition processbecause it provides greater conductivity and resistivity of the platedsubstrate. Unlike vacuum vapor deposition, the sputter coatingdeposition and the ion-beam deposition processes, filaments, fibers,yarns and fabrics (woven, knitted, and non-woven) that have been metalplated by the autocatalytic process result in three dimensionalcontinuous conductive pathways, while retaining the physical propertiesof the base material. Vacuum vapor deposition and sputter coating areinferior because they plate substrates in two dimensions with subsequentshadows, lack uniformity of the plated metal coatings, and alter theflexibility and conformability of the substrate. Vacuum vapor depositionand sputter coating typically plate substrates in a“line of sight”manner similar to commercial spray painting with compressed air.

Once the fibers are coated with a metal or metal alloy, they can beassembled into yarn, cord, thread, fabric, or combinations thereof, toform a layer of woven, knitted or non-woven fabric. The layers areassembled in any configuration predetermined by the intended aspect ofthe wound dressing. Autocatalytic silver plated fibers, filaments, yarnsand fabrics are commercially available.

The present disclosure comprises a method of manufacturing a dressing,wherein the dressing comprises at least one conductive layer; at leastone absorbent layer; and at least one moisture regulation comprising aplurality of apertures disposed in the moisture regulation layercomprising, a) optionally, creating apertures in the moisture regulationlayer, b) providing the conductive layer and the absorbent layer, c)assembling the absorbent layer, the moisture regulation layer and theconductive layer each on top of the other to form a contiguous fabric,and d) laminating the fabric of step c. The lamination step is performedby methods known in the art, including but not limited to, pressuresensitive adhesives, heat pressure lamination, flame lamination, hotmelt lamination, point embossing, point bonding, spot bonding, sewing,or a combination thereof. The present disclosure also comprises a methodof manufacturing a dressing, wherein the dressing comprises at least oneconductive layer, at least one absorbent layer; and at least onemoisture regulation layer positioned adjacent the absorbent layer oradjacent the conductive layer and comprising a plurality of varyingsized apertures disposed in the moisture regulation layer, a) providingthe conductive layer, the moisture regulation layer, and the absorbentlayer, b) assembling the absorbent layer between the moisture regulationlayer and the conductive layer, c) laminating the fabric of step b, andd) creating apertures in the moisture regulation layer.

Creating apertures comprises making the appropriately sized and shapedapertures in the moisture regulation layer using whatever means willcreate the aperture. Cutting, piercing, premolding the fabric to includethe apertures and similar actions are intended by the term creatingapertures. Lamination is performed by pressure sensitive adhesives, heatpressure lamination, flame lamination, hot melt lamination, pointembossing, point bonding, spot bonding, sewing, or a combinationthereof.

The assembled layers of the woven, knitted or non-woven fabric of thepresent disclosure can be laminated by any manufacturing method known inthe art for assembling layers of 100% conductive metallized fibers,layers of varying ratios of conductive metallized fibers tonon-conductive fibers, layers of absorbent material, semi-permeable orimpermeable film or foam, and backing sheets with pressure sensitiveadhesives. Such methods can include, but are not limited to, heatpressure lamination, flame lamination, hot melt lamination or anycombination thereof. Apertures can be cut in the moisture regulationlayer prior to assembly of the layers, or alternatively, after thelayers are laminated, using any manufacturing methods known in the art.The preferable method for placement of the apertures in the moistureregulation layer or the laminate of the moisture regulation layer, skinadhesive and backing sheet is to cut the apertures after the layers arelaminated.

Advantageously, a kiss cut method with a rotary cutting edge dye can beused to cut through only the moisture regulation layer or laminate ofthe moisture regulation layer, skin adhesive layer and backing sheetwithout disturbing the absorbency pad or wound contact layers.

Alternatively, the moisture regulation layer or laminate of the moistureregulation layer, skin adhesive layer and backing sheet can be cut priorto lamination of the fabric, or the moisture regulation layer can be cutprior to assembly of the dressing. Apertures in the various layers canbe preformed in each layer prior to assembly, or formed in the layerafter manufacture.

One means for laminating and electrically integrating the layers is bypoint embossing or point bonding achieved by passing the fabric betweena pair of niprolls, one roll having a series of spaced pins extendingradially from the roll, and the other roll being flat. As the fabriclayers are passed between the niprolls, the pins press into the fabricand force the fibers of one layer into the interstices of the nextlayer, thus bonding the two layers by fiber-to-fiber interaction forces.Alternatively, the layers can be laminated by adhesives, spot bonded (byultrasonic welding or laser welding) or other techniques known to thoseskilled in the art. An alternative technique for laminating the layersis by sewing them together, optionally with conductive thread,preferably autocatalytic silver nylon plated poly or monofilament silvernylon thread. The conductive laminating thread enhances the overallconductivity of the conductive layer 114 and minimizes the resistance.

The wound dressings of this disclosure are most suitable when sterile.

Preferably the dressings of this disclosure are provided sealed within amicrobe-proof package. The dressing may be rendered sterile, forexample, by gamma radiation.

It has been determined that the silver ion release concentration inaqueous solutions is improved with gamma radiation.

With respect to prior art, the application of metallic and ionic silverin the construction of wound dressings has focused on the anti-microbialaspects of silver and silver ions. The ability of the metallic surfaceto release particles of metallic silver or silver ions was related tothe anti-microbial aspect of the dressing. The volume resistivity andconductivity was not addressed. In the present disclosure, resistivityand conductivity contribute to the capabilities of the wound dressing.

The present disclosure is further illustrated by the following examples,which are not to be construed in any way as imposing limitations uponthe scope thereof. On the contrary, it is to be clearly understood thatresort may be had to various other embodiments, modifications, andequivalents thereof which, after reading the description herein, maysuggest themselves to those skilled in the art without departing fromthe spirit of the present disclosure and/or the scope of the appendedclaims.

EXAMPLES Example 1

A dressing of the present disclosure was used to treat a 45 year oldmale suffering from cutaneous manifestation of “shingles”, Herpes zostervirus unilaterally at the tenth thoracic dermatome measuring 2 inches by3 inches. The patient applied the multilayer wound pad illustrated inFIG. 12 after moistening the pad with tap water. The dressing was heldin place with an adhesive layer and backing sheet Within five minutes,the patient reported 25% reduction in pain and within 2 hours nearly 90%reduction in pain. The patient reported that as the dressing dried outthe pain returned, but never returned to the level experienced prior toplacement of the dressing. When the dressing was re-moistened withwater, the pain level was significantly reduced within ten minutes. Thedressing was moistened through the moisture regulation layer withoutremoving the dressing from the cutaneous viral outbreaks. The cutaneouslesions healed within 36 hours after application.

Example 2

A three year old female received 80% total body surface area fullthickness (third degree burns) burns secondary to a flame injury. Shewas taken to surgery shortly after admission and all body surface areaswere debrided of necrotic tissue. Integral synthetic skin was appliedand covered with the wound dressing illustrated in FIG. 12. The dressingwas changed every two days leaving the synthetic skin in place.Gradually the synthetic skin was surgically excised and meshed splitthickness skin graphs were applied. The wound dressing was applied overthe meshed split thickness skin graphs, and was changed every two daysuntil the wounds healed. The dressing was moistened every 12 hours withsterile water throughout the course of healing.

Example 3

Table 1 illustrates the release of silver ions. A four inch by four inchsquare of an autocatalytic electroless silver plated 5.5 ounce persquare yard warp knit fabric was incubated in tryptic soy broth at 37°C. The concentration of silver ions was measured inductively coupledplasma spectroscopy over a twelve day period. FIG. 8 illustrates thatthe concentration of silver ions increased from less than 10micrograms/ml the first hour, to over 60 micrograms/ml by day 5.

TABLE 1 Time 2 3 5 8 12 Dressing 1 Hr 2 Hr 4 Hr 24 Hr Day Day Day DayDay 4 inch 8.5 13.9 19.1 43.1 51.9 58.1 65.4 64.5 64.2 by 4 μg/ml μg/mlμg/ml μg/ml μg/ml μg/ml μg/ml μg/ml μg/ml inch 5.5 oz/yd²

It is well known that between 3 and 25 micrograms/milliliter of ionicsilver are required to kill the most common pathologic woundmicroorganisms. Results indicated that the effective silver ionconcentration was attained in about 1 to about 4 hours.

Example 4

FIG. 9 and Table 2 demonstrate the anti-microbial activity of a fourinch by four inch sample of autocatalytically silver plated 5.5 ounceper square yard warp knit fabric. The fabric was positioned on mediathat was inoculated with pathogenic organisms Pseudomonas aeuroginosaand Staphylococcus aureus and incubated at 37° C. Growth of theorganisms were measured by the “ASTM Standard Test Method forDetermining the Antimicrobial Activity of Immobilized Anti-microbialAgents Under Dynamic Contact Conditions” ASTM E 2149-01. The reductionin CFU/ml from 10⁶ CFU/ml of Pseudomonas aeuroginosa ATCC 9027 andStaphylococcus aureus (MRSA) ATCC 33591 was studied.

The reduction in organism counts expressed in colony forming units (CFU)per milliliter was measured at 0 hours, ½ hour, 1 hour, 1½ hour, 2 hoursand 4 hours.

TABLE 2 Bacterial Time Species 0 Hour 0.5 Hour 1.0 Hour 1.5 Hour 2.0Hour 4.0 Hour Staphylococcus 1,500,000 210,000 3,400 2,500 120 0 aureusCFU/ml CFU/ml CFU/ml CFU/ml CFU/ml MRSA ATCC 33591 Pseudomonas 2,400,0000 0 0 0 0 aeruginosa CFU/ml CFU/ml CFU/ml CFU/ml CFU/ml CFU/ml ATCC 9027

Example 5

A study was conducted to determine the efficacy of a wound dressing ofthe present disclosure when used with Integra®, an artificial skin usedfor burn treatment.

A wound dressing was constructed comprising autocatalytic plated silverfibers for the conductive layer, and one layer of absorbent material waspositioned between the conductive layer and the moisture regulationlayer. The moisture regulation layer was constructed of a polyurethanefilm with 5 mm slit-shaped apertures cut into the layer.

The Integra® was prepared according to the manufacturer's directions toremove the EtOH preservative, and was cut into squares of 1.5 inches.Ten squares were used to test Staphylococcus aureus and ten squares wereused for Pseudomonas aeruginosa.

A seam was created in each square to simulate two pieces of Integralbeing joined together to cover a wound. Each Integral piece was centeredon an individual standard blood agar plate. Each piece of Integra® wascompletely covered with a 2 inch square piece of wound dressing of thepresent disclosure and incubated at 37° C. for 24 hours. At 24 hours,two drops (100 microliters) of a suspension containing greater than 10⁵,colony forming units per milliliter of Pseudomonas aeruginosa orStaphylococcus aurous were added to the center of each dressing,simulating contamination in the post-operative patient. The dressingswere re-moistened and incubated for 48 hours. After 48 hours, thedressings and the Integral were carefully removed using steriletechnique. Cultures were obtained from the area of the plate that wasonce covered with Integra, being sure to swab across the area where theseam in the product had been. Fresh agar plates were streaked with thesesamples and incubated for 24 hours.

The results are noted in the chart below.

TABLE 3 Staphylococcus aureus (MRSA). Pseudomonas aeruginosa Time+growth −growth +growth −growth 72 Hr 6 plates 4 plates 3 plates 7plates

The results illustrated that, when used in conjunction with Integralartificial skin, the wound dressing of the present disclosure was 70%effective in preventing growth of Pseudomonas aeruginosa and 40%effective in preventing growth of Staphylococcus aureus.

Example 6

A test was conducted to determine the anti-microbial efficacy of a wounddressing of the present disclosure in an in vitro setting. Blood agarplates streaked with broth containing 10⁶ CFU per milliliter ofPseudomonas aeruginosa and Methicillin Resistant Staphylococcus aureus(MRSA) were tested.

A wound dressing of the present disclosure was constructed comprisingautocatalytically plated silver fibers for the conductive layer, and onelayer of absorbent material was positioned between the conductive layerand the moisture regulation layer. The moisture regulation layer wasconstructed of a polyurethane film with 5 mm slit-shaped apertures cutinto the layer.

Ten blood agar plates were streaked with broth containing 10⁶ CFU ofPseudomonas aeruginosa and ten blood agar plates were streaked withbroth containing 10⁶ CFU of Methicillin Resistant Staphylococcus aureus(MRSA). One inch square of the wound dressing of the present disclosurewas placed in the center of each of ten blood agar plates. The remainingfive plates were used as controls. The plates were incubated at 37° C.and sterile water added as needed to maintain moist dressings. After 72hours, a culture was obtained from under each dressing and plated onblood agar. These plates were then incubated for 24 hours and evaluatedfor bacterial growth. This process was repeated after six days.

The results of bacterial growth were counted and recorded in the tablebelow.

TABLE 4 Staphylococcus aureus (MRSA). Pseudomonas aeruginosa Time+growth −growth +growth −growth 72 Hr 4 plates 4 plates 4 plates 4plates 6 Days 0 plates 5 plates 0 plates 5 plates

The conclusion was that the wound dressing was effective in killingMethicillin Resistant Staphylococcus aureus (MRSA) and Pseudomonasaeruginosa.

Prolonged exposure to established bacterial growth resulted inprogressive death.

Example 7

The effectiveness of warp knit silver nylon fabric (specific resistanceabout 1Ω/cm²) in inhibiting the growth of three common strains ofbacteria (S. aureus, E. coli and P. aeuginosa) was tested in vitro. Thebacterial cultures were planted in agar-filled petri dishes using theKirby Bauer technique, one culture per dish. Sterilized 1-cm squares ofthe fabric were placed on the surfaces of the cultures. Everytwenty-four hours, each fabric square was removed from the culturemedium and replanted in a different area of the same dish. After 72hours, the culture medium directly underneath the fabric squares wasclear (i.e., the bacteria in those regions had been killed). Inaddition, all areas where the fabric squares had been placed previouslyremained clear.

Example 8

The warp knit silver nylon fabric of Example 7 was found to causededifferentiation of mammalian cell in vitro. The observed effects wereproportional to the concentration of silver ions in the culture mediumand inversely proportional to distance from the fabric: the closer tothe fabric, the greater the concentration of dedifferentiated cells andthe greater the silver ion concentration.

Example 9

The effectiveness of silver sulfadiazine cream, silver nylon fabric, andplain nylon fabric in inhibiting the bacterial growth was compared (L.Smee, “The Effectiveness of Silver Nylon Cloth and Silver SulfadiazineCream as Antiseptics,” Piedmont College Senior Thesis, April, 1996).Five common strains of bacteria were studied including two gram-negativestrains (E. coli, P. aeruginosa) and three gram-positive strains (E.faecalis, S. aureus, S. pyogenes).

Each strain of bacterium was inoculated into three agar-filled petridishes. Following the inoculation, three fabric disks were placed intoeach dish: a disk of plain nylon cloth which served as a control, a diskof silver nylon fabric, and a plain nylon disk which has been coatedwith silver sulfadiazine cream. Each disk had a surface area of 3.4 mm².The dishes were incubated for seventy-two hours, and removed everytwenty-four hours to measure the inhibition zone around each disk (i.e.,the distance from the outer edge of the fabric disk to the perimeter ofthe clear zone of the inhibited bacterial growth about the disk).

Results indicated that the silver nylon fabric and silver sulfadiazinecream were effective bacterial grown inhibitors against all testedstrains. Average results for two trials are listed in Table 5.

-   -   Table 5. inhibition zones (mm) for silver nylon fabric (Ag        Nylon), nylon fabric with silver sulfadiazine cream (Nylon+Ag        Cream), and plain nylon fabric (Nylon). Results shown represent        the average of two trials.

TABLE 5 Nylon + Ag Ag Nylon Cream Nylon E. coli Day 1 7.4 6.3 -0- Day 29.2 6.4 -0- Day 3 10 7.2 -0- P. aeruginosa Day 1 57 32 -0- Day 2 59 29-0- Day 3 62 29 -0- E. faecalis Day 1 8.9 4.0 -0- Day 2 11 3.8 -0- Day 315 2.4 -0- S. aureus Day 1 9.3 7.1 -0- Day 2 9.5 2.1 -0- Day 3 12 0.9-0- S. pyogenes Day 1 57 28 -0- Day 2 66 34 -0- Day 3 70 38 -0-

These results indicate that silver nylon fabric is an effectiveantimicrobial agents. In Example 8, the fabric proved to be moreeffective than silver sulfadiazine cream, creating and maintaining alarger inhibition zone for each strain tested for the duration of theexperiments.

As a delivery system for silver, a fabric with a sufficiently highconcentration of silver releases silver ions at a steady rate for aslong as the fabric is in contact with the culture medium (in vitro or invivo). Such a fabric does not cause allergic reactions, thus, its useprevents other potentially-harmful side effects associated with otherdelivery systems (silver sulfadiazine, silver thiosulfate). A multilayerdressing using the fabric is nonhazardous, conformable to the shape ofthe site to be treated, readily adaptable to diverse clinicalsituations, and safe and easy to use. When treating patients withextensive burns, a dressing according to the disclosure is lessexpensive, less cumbersome, and more effective than silver sulfadiazinecream.

It will be apparent to those skilled in the art that many changes andsubstitutions can be made to the preferred embodiment herein describedwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims.

What is claimed is:
 1. A device comprising: a conductive fabric comprising a) fibers uniformly coated with metallic silver, wherein the fibers comprise multiple filaments uniformly coated with metallic silver; b) non-coated elastomer fibers; c) a surface resistance of 0.001 to 10 ohms/cm²; and d) a plurality of apertures effective to allow liquids and gases to pass through the device, wherein the conductive fabric passively releases an effective amount of ionic silver into a wound to reduce or maintain the microorganism population of the wound to less than 10⁵CFU/ml.
 2. The device of claim 1, wherein the device has a liquid wicking value of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or more.
 3. The device of claim 1, wherein the apertures have an average diameter of less than about 0.2 microns.
 4. The device of claim 1, wherein the device comprises approximately 5 to about 40 wt. % silver.
 5. The device of claim 1, wherein the surface resistance is no greater than approximately 5 ohms/cm².
 6. The device of claim 1, wherein the surface resistance is no greater than approximately 1 ohm/cm².
 7. The device of claim 1, wherein the fabric comprises one or more polymers, yarns, foams, or combinations thereof
 8. The device of claim 7, wherein the one or more yarns comprises a synthetic polymer fiber and an elastic component.
 9. The device of claim 8, wherein the elastic component comprises a long-chain synthetic polymer comprising at least 85% of a segmented polyurethane.
 10. The device of claim 9, wherein the elastic component is not coated with the anti-microbial metal.
 11. The device of claim 9, wherein the elastic component is wrapped around the synthetic polymer fiber.
 12. The device of claim 11, wherein the synthetic polymer fiber comprises nylon.
 13. The device of claim 1, further comprising a second layer.
 14. The device of claim 13, wherein the second layer comprises a second layer of conformable, conductive fabric.
 15. The device of claim 14, wherein the second layer of conformable conductive fabric is separated from the first conformable, conductive fabric by a plurality of supports.
 16. The device of claim 15, wherein the supports comprise nylon.
 17. The device of claim 15, wherein the supports are not coated with an anti-microbial metal.
 18. The device of claim 16, wherein the nylon supports are uniformly coated with silver.
 19. The device of claim 7, wherein the substrate comprises woven or knitted fibers or yarns.
 20. The device of claim 7, wherein the substrate comprises non-woven fibers or yarns.
 21. The device of claim 14, further comprising a third layer adjacent to said second layer, said third layer made of an air-permeable material.
 22. The device of claim 14, further comprising a third layer adjacent to said second layer, said third layer made of a water-permeable material.
 23. The device of claim 1, wherein the device maintains a transepithelial electrical potential of a wound at about −10 mvolts to about −70 mvolts.
 24. The device of claim 1, wherein the device is configured to reduce a wound potential by about 0.1 mV to about 20 mV.
 25. The wound dressing of claim 1, wherein ionic silver released into the pathology reduces and maintains the microorganism population of the pathology by at least two log units over a period of 24 hours to accelerate or enhance wound healing of the pathology.
 26. The wound dressing of claim 1 wherein the microorganism population comprises bacteria.
 27. The wound dressing of claim 1, wherein the microorganism population comprises fungi.
 28. The wound dressing of claim 1, wherein the effective amount of ionic silver is released into the pathology for at least three days.
 29. The wound dressing of claim 1 wherein the elastomer comprises a polyurethane-polyurea copolymer.
 30. The wound dressing of claim 1 wherein the fabric is a knit fabric, woven fabric, twisted and knotted fabric, non-woven fabric, or compound/complex fabric.
 31. A medical device comprising: a conductive fabric comprising a) fibers uniformly coated with metallic silver, wherein the fibers comprise multiple filaments uniformly coated with metallic silver; b) non-coated elastomer fibers; c) a surface resistance of 0.001 to 10 ohms/cm²; and d) a plurality of apertures effective to allow liquids and gases to pass through the device, wherein the conductive fabric passively releases more than 3 μg/ml of ionic silver in about 1 hour when in contact with fluid exudate. 